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Lejosne S and Mozer FS (2016), "Van Allen Probe measurements of the electric drift E×B/B2 at Arecibo's L=1.4 field-line coordinate", Geophysical Research Letters. , pp. n/a-n/a.
Abstract: We have used electric and magnetic measurements by Van Allen Probe B from 2013 to 2014 to examine the equatorial electric drift ExB/B2 at one field-line coordinate set to Arecibo's incoherent scatter radar location (L?=?1.43). We report on departures from the traditional picture of corotational motion with the Earth in two ways: (1) the rotational angular speed is found to be 10% smaller than the rotational angular speed of the Earth, in agreement with previous works on plasmaspheric notches, and (2) the equatorial electric drift displays a dependence in magnetic local time, with a pattern consistent with the mapping of the Arecibo ionosphere dynamo electric fields along equipotential magnetic field lines. The electric fields due to the ionosphere dynamo are therefore expected to play a significant role when discussing for instance the structure and dynamics of the plasmasphere or the transport of trapped particles in the inner belt.
BibTeX:
@article{GRL:GRL54697,
  author = {Lejosne, Solène and Mozer, F. S.},
  title = {Van Allen Probe measurements of the electric drift E×B/B2 at Arecibo's L=1.4 field-line coordinate},
  journal = {Geophysical Research Letters},
  year = {2016},
  pages = {n/a--n/a},
  note = {2016GL069875},
  url = {http://dx.doi.org/10.1002/2016GL069875},
  doi = {10.1002/2016GL069875}
}
Gong Y, Zhou Q and Zhang S (2016), "A study on electric field mapping from the F region to the E region at Arecibo", Journal of Geophysical Research: Space Physics., January, 2016. Vol. 121(1), pp. 713-718.
Abstract: We present the first direct comparison of the vertical electric fields in the E and F regions at Arecibo. The electric field is generally assumed to be height invariant and can be mapped from the F region to the E region along the magnetic field line. We develop a method to verify the electric field mapping by comparing the E and F region eastward ion drifts at heights where the E region vertical ion drift is zero. Our method avoids using the ion-neutral collision frequency, which is considered to be the most uncertain parameter in computing the E region electric field using radar measurements. The results show that the F region eastward E?×?B ion drift and the E region eastward ion drift at locations where vertical ion drift equals zero are not consistent. This implies that the E region vertical electric field is not the same as that from the F region.
BibTeX:
@article{JGRA:JGRA52335,
  author = {Gong, Yun and Zhou, Qihou and Zhang, Shaodong},
  title = {A study on electric field mapping from the F region to the E region at Arecibo},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2016},
  volume = {121},
  number = {1},
  pages = {713--718},
  url = {http://dx.doi.org/10.1002/2015JA022035},
  doi = {10.1002/2015JA022035}
}
Park J, Martinis CR, Lühr H, Pfaff RF and Kwak Y-S (2016), "Hemispheric asymmetry in transition from equatorial plasma bubble to blob as deduced from 630.0 nm airglow observations at low latitudes", Journal of Geophysical Research: Space Physics. Vol. 121(1), pp. 881-893.
Abstract: Transitions from depletions to enhancements of 630.0 nm nighttime airglow have been observed at Arecibo. Numerical simulations by Krall et al. (2009) predicted that they should occur only in one hemisphere, which has not yet been confirmed observationally. In this study we investigate the hemispheric conjugacy of the depletion-to-enhancement transition using multiple instruments. We focus on one event observed in the American longitude sector on 22 December 2014: 630.0 nm airglow depletions evolved into enhancements in the Northern Hemisphere while the evolution did not occur in the conjugate location in the Southern Hemisphere. Concurrent plasma density measured by low Earth orbit (LEO) satellites and 777.4 nm airglow images support that the depletions and enhancements of 630.0 nm nighttime airglow reflect plasma density decreases and increases (blobs), respectively. Characteristics of the airglow depletions, in the context of the LEO satellite data, further suggest that the plasma density depletion deduced from the airglow data represents equatorial plasma bubbles (EPBs) rather than medium-scale traveling ionospheric disturbances from midlatitudes. Hence, the event in this study can be interpreted as EPB-to-blob transition.
BibTeX:
@article{JGRA:JGRA52385,
  author = {Park, Jaeheung and Martinis, Carlos R. and Lühr, Hermann and Pfaff, Robert F. and Kwak, Young-Sil},
  title = {Hemispheric asymmetry in transition from equatorial plasma bubble to blob as deduced from 630.0 nm airglow observations at low latitudes},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2016},
  volume = {121},
  number = {1},
  pages = {881--893},
  note = {2015JA022175},
  url = {http://dx.doi.org/10.1002/2015JA022175},
  doi = {10.1002/2015JA022175}
}
Gong Y, Zhou Q, Zhang S, Aponte N and Sulzer M (2016), "An incoherent scatter radar study of the midnight temperature maximum that occurred at Arecibo during a sudden stratospheric warming event in January 2010", Journal of Geophysical Research: Space Physics. , pp. n/a-n/a.
Abstract: We present an analysis of the thermospheric midnight temperature maximum, a large increment of temperature around midnight. The analysis is based on data collected from the Arecibo incoherent scatter radar during 14–21 January 2010. The experiment overlaps with a major sudden stratospheric warming (SSW) event which commenced on 18 January 2010. Throughout the observation, the ion temperature exhibited moderate increase around postmidnight during 14–17 January, while it showed more intense increment during 18–21 January. In particular, on 20 January, the amplitude of the midnight temperature maximum (MTM) is 310?K, which is seldom seen at Arecibo. During the SSW, the meridional wind reverses toward the pole just before the commencement of the MTM. Then, the poleward wind and the ion temperature maximize almost at the same time. The variation of meridional wind and the MTM are consistent with the Whole Atmosphere Model (WAM) studies, which suggested that the variation is due to effects from an upward propagating terdiurnal tide. On the nights of 18–19 January, the MTM showed clear phase variation at the heights of 265, 303, and 342?km. A strong terdiurnal tide has been observed during the SSW and it is likely generated from low atmosphere and propagating upward. Our results provide direct observational evidence that the propagating upward terdiurnal tide plays an important role in causing the MTM, which supports the WAM simulations.
BibTeX:
@article{JGRA:JGRA52648,
  author = {Gong, Yun and Zhou, Qihou and Zhang, Shaodong and Aponte, Nestor and Sulzer, Michael},
  title = {An incoherent scatter radar study of the midnight temperature maximum that occurred at Arecibo during a sudden stratospheric warming event in January 2010},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2016},
  pages = {n/a--n/a},
  note = {2016JA022439},
  url = {http://dx.doi.org/10.1002/2016JA022439},
  doi = {10.1002/2016JA022439}
}
Yue X, Zhou Q, Yi F, Friedman J, Raizada S and Tepley C (2016), "Simultaneous and common-volume lidar observations of K/Na layers and temperature at Arecibo Observatory (18°N, 67°W)", Journal of Geophysical Research: Atmospheres. , pp. n/a-n/a.
Abstract: We present the first simultaneous and common-volume observations of mesospheric K and Na densities and temperature conducted by a K Doppler lidar and a Na lidar at the Arecibo Observatory (18.35°N, 66.75°W), Puerto Rico. Measurements reported here were conducted on three nights with 9, 6, and 7?h of observations in December 2003 and January 2004. The behaviors of the Na and K layer and the temperature variations showed that the bottom edges of the Na and K layers matched one another almost exactly. Layer peak and column densities increased/decreased together with temperature for the Na layer, but not for the K layer. The correlation between temperature and density fluctuations was strongly positive at and just below the peak altitude of the nightly mean density profile but transitioned to negative several kilometers above the respective peak of either Na or K. The peak densities of the sporadic Na and K layers occurring at low altitudes did not behave in the same manner especially when the background temperature decreased. We discuss, qualitatively, the impact of dynamical and chemical effects on the behaviors of the Na and K layers. Our analysis suggests that wave-induced dynamical transport can account for the observed correlations between temperature, Na density, and K density fluctuations. Dynamical transport and wave-induced chemical transport have similar effects on the behaviors of the Na and K layers. The resulting differences in Na and K layers are qualitatively consistent with different dependences on temperature of the Na and K chemistries.
BibTeX:
@article{JGRD:JGRD53093,
  author = {Yue, Xianchang and Zhou, Qihou and Yi, Fan and Friedman, Jonathan and Raizada, Shikha and Tepley, Craig},
  title = {Simultaneous and common-volume lidar observations of K/Na layers and temperature at Arecibo Observatory (18°N, 67°W)},
  journal = {Journal of Geophysical Research: Atmospheres},
  year = {2016},
  pages = {n/a--n/a},
  note = {2015JD024494},
  url = {http://dx.doi.org/10.1002/2015JD024494},
  doi = {10.1002/2015JD024494}
}
Hajra R, Chakraborty SK, Tsurutani BT, DasGupta A, Echer E, Brum CG, Gonzalez WD and Sobral JHA (2016), "An empirical model of ionospheric total electron content (TEC) near the crest of the equatorial ionization anomaly (EIA)", Journal of Space Weather and Space Climate. Vol. 6, pp. A29.
Abstract: We present a geomagnetic quiet time (Dst > ?50 nT) empirical model of ionospheric total electron content (TEC) for the northern equatorial ionization anomaly (EIA) crest over Calcutta, India. The model is based on the 1980–1990 TEC measurements from the geostationary Engineering Test Satellite-2 (ETS-2) at the Haringhata (University of Calcutta, India: 22.58° N, 88.38° E geographic; 12.09° N, 160.46° E geomagnetic) ionospheric field station using the technique of Faraday rotation of plane polarized VHF (136.11 MHz) signals. The ground station is situated virtually underneath the northern EIA crest. The monthly mean TEC increases linearly with F10.7 solar ionizing flux, with a significantly high correlation coefficient (r = 0.89–0.99) between the two. For the same solar flux level, the TEC values are found to be significantly different between the descending and ascending phases of the solar cycle. This ionospheric hysteresis effect depends on the local time as well as on the solar flux level. On an annual scale, TEC exhibits semiannual variations with maximum TEC values occurring during the two equinoxes and minimum at summer solstice. The semiannual variation is strongest during local noon with a summer-to-equinox variability of ~50–100 TEC units. The diurnal pattern of TEC is characterized by a pre-sunrise (0400–0500 LT) minimum and near-noon (1300–1400 LT) maximum. Equatorial electrodynamics is dominated by the equatorial electrojet which in turn controls the daytime TEC variation and its maximum. We combine these long-term analyses to develop an empirical model of monthly mean TEC. The model is validated using both ETS-2 measurements and recent GNSS measurements. It is found that the present model efficiently estimates the TEC values within a 1-? range from the observed mean values.
BibTeX:
@article{refId0,
  author = {Hajra, Rajkumar and Chakraborty, Shyamal Kumar and Tsurutani, Bruce T. and DasGupta, Ashish and Echer, Ezequiel and Brum, Christiano G.M. and Gonzalez, Walter D. and Sobral, José Humberto Andrade},
  title = {An empirical model of ionospheric total electron content (TEC) near the crest of the equatorial ionization anomaly (EIA)},
  journal = {Journal of Space Weather and Space Climate},
  year = {2016},
  volume = {6},
  pages = {A29},
  url = {http://dx.doi.org/10.1051/swsc/2016023},
  doi = {10.1051/swsc/2016023}
}
Wang S, Huang S, Fang H and Wang Y (2016), "Evaluation and correction of theIRI2016 topside ionospheric electron density model", Advances in Space Research . Vol. 58(7), pp. 1229 - 1241.
Abstract: Abstract The international reference ionosphere (IRI) is the internationally recommended empirical model. The IRI2016 is now the latest version, and it includes three options for the prediction of topside electron density profiles: IRI2001, a correction of IRI2001 (IRI2001corr), and NeQuick model. In the paper, we use the Arecibo, Jicamarca, and Millstone Hill incoherent scatter radar observed topside electron density data ranging from year 2001 to 2014 to assess the prediction capabilities of these three model options. The results show that the NeQuick model outputs perform best at these areas from the point view of relative difference distribution, followed by the IRI2001corr model, and the IRI2001 option is worst. To further improve the performance of NeQuick and IRI2001corr options, the correction factors are introduced in their model formulation and are determined by the least squares estimation technique. Compared with the original models, the corrected models perform in average better, especially at low and medium solar activities.
BibTeX:
@article{Wang20161229,
  author = {Sicheng Wang and Sixun Huang and Hanxian Fang and Yu Wang},
  title = {Evaluation and correction of theIRI2016 topside ionospheric electron density model},
  journal = {Advances in Space Research },
  year = {2016},
  volume = {58},
  number = {7},
  pages = {1229 - 1241},
  url = {http://www.sciencedirect.com/science/article/pii/S0273117716303350},
  doi = {10.1016/j.asr.2016.06.020}
}
Abdu MA, Brum CG, Batista PP, Gurubaran S, Pancheva D, Bageston JV, Batista IS and Takahashi H (2015), "Fast and ultrafast Kelvin wave modulations of the equatorial evening F region vertical drift and spread F development", Earth, Planets and Space., Jan, 2015. Vol. 67(1)
Abstract: In this paper, we investigate the role of eastward and upward propagating fast (FK) and ultrafast Kelvin (UFK) waves in the day-to-day variability of equatorial evening prereversal vertical drift and post sunset generation of spread F/plasma bubble irregularities. Meteor wind data from Cariri and Cachoeira Paulista (Brazil) and medium frequency (MF) radar wind data from Tirunelveli (India) are analyzed together with Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics/Sounding of the Atmosphere using Broadband Emission Radiometry (TIMED/SABER) temperature in the 40- to 100-km region to characterize the zonal and vertical propagations of these waves. Also analyzed are the F region evening vertical drift and spread F (ESF) development features as diagnosed by Digisonde (Lowell Digisonde International, LLC, Lowell, MA, USA) operated at Fortaleza and Sao Luis in Brazil. The SABER temperature data permitted determination of the upward propagation characteristics of the FK (E1) waves with propagation speed in the range of 4 km/day. The radar mesosphere and lower thermosphere (MLT) winds in the widely separated longitude sectors have yielded the eastward phase velocity of both the FK and UFK waves. The vertical propagation of these waves cause strong oscillation in the F region evening prereversal vertical drift, observed for the first time at both FK and UFK periodicities. A delay of a few (approximately 10) days is observed in the F region vertical drift perturbation with respect to the corresponding FK/UFK zonal wind oscillations, or temperature oscillations in the MLT region, which has permitted a direct identification of the sunset electrodynamic coupling process as being responsible for the generation of the FK/UFK-induced vertical drift oscillation. The vertical drift oscillations are found to cause significant modulation in the spread F/plasma bubble irregularity development. The overall results highlight the role of FK/UFK waves in the day-to-day variability of the ESF in its occurrence season.
BibTeX:
@article{Abdu2015,
  author = {Abdu, Mangalathayil A and Brum, Christiano GM and Batista, Paulo P and Gurubaran, Subramanian and Pancheva, Dora and Bageston, Jose V and Batista, Inez S and Takahashi, Hisao},
  title = {Fast and ultrafast Kelvin wave modulations of the equatorial evening F region vertical drift and spread F development},
  journal = {Earth, Planets and Space},
  year = {2015},
  volume = {67},
  number = {1},
  url = {http://dx.doi.org/10.1186/s40623-014-0143-5},
  doi = {10.1186/s40623-014-0143-5}
}
Djuth FT and DuBois DF (2015), "Temporal Development of HF-Excited Langmuir and Ion Turbulence at Arecibo", Earth, Moon, and Planets. Vol. 116(1), pp. 19-53.
Abstract: The Arecibo high-power, high-frequency (HF) facility and 430 MHz radar are used to examine the temporal development of the HF-induced Langmuir and ion turbulences from 1 ms to many minutes after the turn-on of the HF beam in the F region. All HF observations begin in a smooth, stratified, stable plasma. ``Cold start'' HF transmissions are employed to avoid remnant irregularities from prior HF transmissions. HF-excited plasma line (HFPL) and ion line echoes are used to monitor the evolution of the turbulence. In the evening/nighttime the HFPL develops in three reproducible stages. Over time scales of 0 to 10--20 ms (possibly 40 ms), the smooth plasma conditions are maintained, and the results are consistent with theoretical models of the excitation of strong Langmuir turbulence near HF reflection. This entails the initiation of the so-called ``caviton production cycle.'' The turbulence from the parametric decay instability is detected at lower altitudes where the radar wave vector matches those of the HF-enhanced waves. The data suggests that the two processes coexist in the region in between. After textasciitilde40 ms the ``overshoot process'' begins and consists of a downward extension of the HFPL from the HF reflection region to heights textasciitilde1.1 km below followed by a retreat back to the reflection region. The whole overshoot process takes place over a time scale of textasciitilde3 s. Thereafter the echo remains near HF reflection for 20--90 s after HF turn-on. The HFPL echo subsequently breaks up into patches because of the formation of large-scale electron density structures in the plasma. New kinetic models indicate that suprathermal electrons excited in the plasma by, for example, caviton burn-out serve to regulate plasma turbulence in the modified ionospheric volume.
BibTeX:
@article{Djuth2015,
  author = {Djuth, F. T.
and DuBois, D. F.}, title = {Temporal Development of HF-Excited Langmuir and Ion Turbulence at Arecibo}, journal = {Earth, Moon, and Planets}, year = {2015}, volume = {116}, number = {1}, pages = {19--53}, url = {http://dx.doi.org/10.1007/s11038-015-9458-x}, doi = {10.1007/s11038-015-9458-x} }
Djuth F and DuBois D (2015), "Erratum to: Temporal Development of HF-Excited Langmuir and Ion Turbulence at Arecibo", Earth, Moon, and Planets. Vol. 116(2), pp. 139-139. Springer.
BibTeX:
@article{djuth2015erratum,
  author = {Djuth, FT and DuBois, DF},
  title = {Erratum to: Temporal Development of HF-Excited Langmuir and Ion Turbulence at Arecibo},
  journal = {Earth, Moon, and Planets},
  publisher = {Springer},
  year = {2015},
  volume = {116},
  number = {2},
  pages = {139--139}
}
Drob DP, Emmert JT, Meriwether JW, Makela JJ, Doornbos E, Conde M, Hernandez G, Noto J, Zawdie KA, McDonald SE, Huba JD and Klenzing JH (2015), "An update to the Horizontal Wind Model (HWM): The quiet time thermosphere", Earth and Space Science. Vol. 2(7), pp. 301-319.
Abstract: The Horizontal Wind Model (HWM) has been updated in the thermosphere with new observations and formulation changes. These new data are ground-based 630?nm Fabry-Perot Interferometer (FPI) measurements in the equatorial and polar regions, as well as cross-track winds from the Gravity Field and Steady State Ocean Circulation Explorer (GOCE) satellite. The GOCE wind observations provide valuable wind data in the twilight regions. The ground-based FPI measurements fill latitudinal data gaps in the prior observational database. Construction of this reference model also provides the opportunity to compare these new measurements. The resulting update (HWM14) provides an improved time-dependent, observationally based, global empirical specification of the upper atmospheric general circulation patterns and migrating tides. In basic agreement with existing accepted theoretical knowledge of the thermosphere general circulation, additional calculations indicate that the empirical wind specifications are self-consistent with climatological ionosphere plasma distribution and electric field patterns.
BibTeX:
@article{ESS2:ESS224,
  author = {Drob, Douglas P. and Emmert, John T. and Meriwether, John W. and Makela, Jonathan J. and Doornbos, Eelco and Conde, Mark and Hernandez, Gonzalo and Noto, John and Zawdie, Katherine A. and McDonald, Sarah E. and Huba, Joe D. and Klenzing, Jeff H.},
  title = {An update to the Horizontal Wind Model (HWM): The quiet time thermosphere},
  journal = {Earth and Space Science},
  year = {2015},
  volume = {2},
  number = {7},
  pages = {301--319},
  note = {2014EA000089},
  url = {http://dx.doi.org/10.1002/2014EA000089},
  doi = {10.1002/2014EA000089}
}
Park J, Stolle C, Xiong C, Lühr H, Pfaff RF, Buchert S and Martinis CR (2015), "A dayside plasma depletion observed at midlatitudes during quiet geomagnetic conditions", Geophysical Research Letters. Vol. 42(4), pp. 967-974.
Abstract: In this study we investigate a dayside, midlatitude plasma depletion (DMLPD) encountered on 22 May 2014 by the Swarm and GRACE satellites, as well as ground-based instruments. The DMLPD was observed near Puerto Rico by Swarm near 10 LT under quiet geomagnetic conditions at altitudes of 475–520?km and magnetic latitudes of ?25°–30°. The DMLPD was also revealed in total electron content observations by the Saint Croix station and by the GRACE satellites (430?km) near 16?LT and near the same geographic location. The unique Swarm constellation enables the horizontal tilt of the DMLPD to be measured (35° clockwise from the geomagnetic east-west direction). Ground-based airglow images at Arecibo showed no evidence for plasma density depletions during the night prior to this dayside event. The C/NOFS equatorial satellite showed evidence for very modest plasma density depletions that had rotated into the morningside from nightside. However, the equatorial depletions do not appear related to the DMLPD, for which the magnetic apex height is about 2500?km. The origins of the DMLPD are unknown, but may be related to gravity waves.
BibTeX:
@article{GRL:GRL52558,
  author = {Park, Jaeheung and Stolle, Claudia and Xiong, Chao and Lühr, Hermann and Pfaff, Robert F. and Buchert, Stephan and Martinis, Carlos R.},
  title = {A dayside plasma depletion observed at midlatitudes during quiet geomagnetic conditions},
  journal = {Geophysical Research Letters},
  year = {2015},
  volume = {42},
  number = {4},
  pages = {967--974},
  url = {http://dx.doi.org/10.1002/2014GL062655},
  doi = {10.1002/2014GL062655}
}
Zhang S-R, Erickson PJ, Foster JC, Holt JM, Coster AJ, Makela JJ, Noto J, Meriwether JW, Harding BJ, Riccobono J and Kerr RB (2015), "Thermospheric poleward wind surge at midlatitudes during great storm intervals", Geophysical Research Letters. Vol. 42(13), pp. 5132-5140.
Abstract: We report a significant poleward surge in thermospheric winds at subauroral and midlatitudes following the 17–18 March 2015 great geomagnetic storm. This premidnight surge is preceded by strong westward winds. These disturbances were observed over three sites with geodetic latitudes 35–42°N in the American sector by Fabry-Perot interferometers at 630?nm wavelength. Prior to the wind disturbances, subauroral polarization streams (SAPS) were measured by the Millstone Hill incoherent scatter radar between 20 and 02?UT. We identify the observed neutral wind variations as driven by SAPS, through a scenario where strong ion flows cause a westward neutral wind, subsequently establishing a poleward wind surge due to the poleward Coriolis force on that westward wind. These regional disturbances appear to have prevented the well-known storm time equatorward wind surge from propagating into low latitudes, with the consequence that the classic disturbance dynamo mechanism failed to occur.
BibTeX:
@article{GRL:GRL53139,
  author = {Zhang, Shun-Rong and Erickson, Philip J. and Foster, John C. and Holt, John M. and Coster, Anthea J. and Makela, Jonathan J. and Noto, John and Meriwether, John W. and Harding, Brian J. and Riccobono, Juanita and Kerr, Robert B.},
  title = {Thermospheric poleward wind surge at midlatitudes during great storm intervals},
  journal = {Geophysical Research Letters},
  year = {2015},
  volume = {42},
  number = {13},
  pages = {5132--5140},
  note = {2015GL064836},
  url = {http://dx.doi.org/10.1002/2015GL064836},
  doi = {10.1002/2015GL064836}
}
Carlson HC, Djuth FT, Perillat P and Sulzer M (2015), "Low Latitude 10s eV electrons: Night Time Plasma Line as a new Research Capability", Geophysical Research Letters. , pp. n/a-n/a.
Abstract: The incoherent scatter radar (ISR) plasma line (PL) in daylight is excited by photoelectrons [Perkins and Salpeter, 1965]. Measurement of its intensity (kTp) has long been used for their study [Yngvesson and Perkins, 1968; Cicerone, 1974]. At night, absent any other excitation mechanism, the PL intensity should have a thermal amplitude level kTe, determined by the electron gas temperature Te. To the contrary Carlson et al. [1982] found nighttime PLs over Arecibo enhanced >3 times above thermal intensities despite the absence of any known causative mechanism. Here we present discovery that nighttime PLs frequently recur, with quite variable enhancement. In the absence of direct solar EUV, these enhanced PLs must be produced by particle precipitation, manifested by the presence of variable recurring F-region ~10s eV electron fluxes. We see this as offering a new tool for space environment studies, opening a new era of particle precipitation research and ISR calibration.
BibTeX:
@article{GRL:GRL53409,
  author = {Carlson, Herbert C. and Djuth, Frank T. and Perillat, Phil and Sulzer, Mike},
  title = {Low Latitude 10s eV electrons: Night Time Plasma Line as a new Research Capability},
  journal = {Geophysical Research Letters},
  year = {2015},
  pages = {n/a--n/a},
  note = {2015GL065172},
  url = {http://dx.doi.org/10.1002/2015GL065172},
  doi = {10.1002/2015GL065172}
}
Zawdie KA, Huba JD, Drob DP and Bernhardt PA (2015), "A coupled ionosphere-raytrace model for high-power HF heating", Geophysical Research Letters. Vol. 42(22), pp. 9650-9656.
Abstract: The first 3-D model of artificial HF ionospheric heating to self-consistently calculate the modification in heating location due to evolving ionospheric gradients has been developed. The model combines the ionosphere model SAMI3/ESF and the HF propagation code MoJo-15. At each time step, the simulated path of the HF wave through the ionosphere is used to determine the HF heating location. These calculations have been used to explain the physical mechanism responsible for the snapback effect observed in an Arecibo HF heating experiment described by Bernhardt et al. (1988). The heater wave is refracted by the density cavity, which causes the heating location to drift in longitude. Eventually, the density cavity convects into the path of the refracted ray, such that only a small portion of the ray is above the threshold for HF heating and the heating location snaps back even though the ray itself is still refracted in longitude.
BibTeX:
@article{GRL:GRL53687,
  author = {Zawdie, K. A. and Huba, J. D. and Drob, D. P. and Bernhardt, P. A.},
  title = {A coupled ionosphere-raytrace model for high-power HF heating},
  journal = {Geophysical Research Letters},
  year = {2015},
  volume = {42},
  number = {22},
  pages = {9650--9656},
  note = {2015GL066673},
  url = {http://dx.doi.org/10.1002/2015GL066673},
  doi = {10.1002/2015GL066673}
}
Hajra R, Tsurutani B, Echer E, Gonzalez W, Brum C, Vieira L and Santolik O (2015), "Relativistic electron acceleration during HILDCAA events: are precursor CIR magnetic storms important?", Earth, Planets and Space. Vol. 67(1) Springer Berlin Heidelberg.
Abstract: We present a comparative study of high-intensity long-duration continuous AE activity (HILDCAA) events, both isolated and those occurring in the “recovery phase” of geomagnetic storms induced by corotating interaction regions (CIRs). The aim of this study is to determine the difference, if any, in relativistic electron acceleration and magnetospheric energy deposition. All HILDCAA events in solar cycle 23 (from 1995 through 2008) are used in this study. Isolated HILDCAA events are characterized by enhanced fluxes of relativistic electrons compared to the pre-event flux levels. CIR magnetic storms followed by HILDCAA events show almost the same relativistic electron signatures. Cluster 1 spacecraft showed the presence of intense whistler-mode chorus waves in the outer magnetosphere during all HILDCAA intervals (when Cluster data were available). The storm-related HILDCAA events are characterized by slightly lower solar wind input energy and larger magnetospheric/ionospheric dissipation energy compared with the isolated events. A quantitative assessment shows that the mean ring current dissipation is ~34 % higher for the storm-related events relative to the isolated events, whereas Joule heating and auroral precipitation display no (statistically) distinguishable differences. On the average, the isolated events are found to be comparatively weaker and shorter than the storm-related events, although the geomagnetic characteristics of both classes of events bear no statistically significant difference. It is concluded that the CIR storms preceding the HILDCAAs have little to do with the acceleration of relativistic electrons. Our hypothesis is that ~10–100-keV electrons are sporadically injected into the magnetosphere during HILDCAA events, the anisotropic electrons continuously generate electromagnetic chorus plasma waves, and the chorus then continuously accelerates the high-energy portion of this electron spectrum to MeV energies.
BibTeX:
@article{Hajra2015,
  author = {Hajra, Rajkumar and Tsurutani, BruceT and Echer, Ezequiel and Gonzalez, WalterD and Brum, ChristianoGarnettMarques and Vieira, LuisEduardoAntunes and Santolik, Ondrej},
  title = {Relativistic electron acceleration during HILDCAA events: are precursor CIR magnetic storms important?},
  journal = {Earth, Planets and Space},
  publisher = {Springer Berlin Heidelberg},
  year = {2015},
  volume = {67},
  number = {1},
  url = {http://dx.doi.org/10.1186/s40623-015-0280-5},
  doi = {10.1186/s40623-015-0280-5}
}
Huang H, Chen Y, Liu L, Le H and Wan W (2015), "An empirical model of the topside plasma density around 600 km based on ROCSAT-1 and Hinotori observations", Journal of Geophysical Research: Space Physics. Vol. 120(5), pp. 4052-4063.
Abstract: It is an urgent task to improve the ability of ionospheric empirical models to more precisely reproduce the plasma density variations in the topside ionosphere. Based on the Republic of China Satellite 1 (ROCSAT-1) observations, we developed a new empirical model of topside plasma density around 600?km under relatively quiet geomagnetic conditions. The model reproduces the ROCSAT-1 plasma density observations with a root-mean-square-error of 0.125 in units of lg(Ni(cm?3)) and reasonably describes the temporal and spatial variations of plasma density at altitudes in the range from 550 to 660?km. The model results are also in good agreement with observations from Hinotori, Coupled Ion-Neutral Dynamics Investigations/Communications/Navigation Outage Forecasting System satellites and the incoherent scatter radar at Arecibo. Further, we combined ROCSAT-1 and Hinotori data to improve the ROCSAT-1 model and built a new model (R&H model) after the consistency between the two data sets had been confirmed with the original ROCSAT-1 model. In particular, we studied the solar activity dependence of topside plasma density at a fixed altitude by R&H model and find that its feature slightly differs from the case when the orbit altitude evolution is ignored. In addition, the R&H model shows the merging of the two crests of equatorial ionization anomaly above the F2 peak, while the IRI_Nq topside option always produces two separate crests in this range of altitudes.
BibTeX:
@article{JGRA:JGRA51813,
  author = {Huang, He and Chen, Yiding and Liu, Libo and Le, Huijun and Wan, Weixing},
  title = {An empirical model of the topside plasma density around 600 km based on ROCSAT-1 and Hinotori observations},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2015},
  volume = {120},
  number = {5},
  pages = {4052--4063},
  note = {2014JA020940},
  url = {http://dx.doi.org/10.1002/2014JA020940},
  doi = {10.1002/2014JA020940}
}
Wu L-L, Zhou QH, Chen T-J, Liang J and Wu X (2015), "Application of particle swarm optimization method to incoherent scatter radar measurement of ionosphere parameters", Journal of Geophysical Research: Space Physics. , pp. n/a-n/a.
Abstract: Simultaneous derivation of multiple ionospheric parameters from the incoherent scatter power spectra in the F1-region is difficult because the spectra have only subtle differences for different combinations of parameters. In this study, we apply a particle swarm optimizer (PSO) to incoherent scatter power spectrum fitting and compare it to the commonly used least square fitting (LSF) technique. The PSO method is found to outperform the LSF method in practically all scenarios using simulated data. The PSO method offers the advantages of not being sensitive to initial assumptions and allowing physical constraints to be easily built into the model. When simultaneously fitting for molecular ion fraction (fm), ion temperature (Ti) and ratio of ion to electron temperature (?T), ?T is largely stable. The uncertainty between fm and Ti can be described as a quadratic relationship. The significance of this result is that Ti can be retroactively corrected for data archived many years ago where the assumption of fm may not be accurate and the original power spectra are unavailable. In our discussion, we emphasize the fitting for fm, which is a difficult parameter to obtain. PSO method is often successful in obtaining fm whereas LSF fails. We apply both PSO and LSF to actual observations made by the Arecibo incoherent scatter radar. The results show that PSO method is a viable method to simultaneously determine ion and electron temperatures and molecular ion fraction when the last is greater than 0.3.
BibTeX:
@article{JGRA:JGRA52063,
  author = {Wu, Li-Li and Zhou, Qihou H. and Chen, Tie-Jun and Liang, J.J. and Wu, Xin},
  title = {Application of particle swarm optimization method to incoherent scatter radar measurement of ionosphere parameters},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2015},
  pages = {n/a--n/a},
  note = {2014JA020970},
  url = {http://dx.doi.org/10.1002/2014JA020970},
  doi = {10.1002/2014JA020970}
}
Dawkins ECM, Plane JMC, Chipperfield MP and Feng W (2015), "The near-global mesospheric potassium layer: Observations and modeling", Journal of Geophysical Research: Atmospheres. Vol. 120(15), pp. 7975-7987.
Abstract: The meteoric metal layers act as unique tracers of chemistry and dynamics in the upper atmosphere. Existing lidar studies from a few locations show that K exhibits a semiannual seasonality (winter and summer maxima), quite unlike the annual seasonality (winter maximum and summer minimum) seen with Na and Fe. This work uses spaceborne observations made with the Optical Spectrograph and InfraRed Imager System instrument on the Odin satellite to retrieve the near-global K layer for the first time. The satellite data (2004 to mid-2013) are used to validate the implementation of a recently proposed potassium chemistry scheme in a whole atmosphere chemistry climate model, which provides a chemical basis for this semiannual seasonal behavior. The satellite and model data show that this semiannual seasonality is near global in extent, with the strongest variation at middle and high latitudes. The column abundance, centroid layer height, and root-mean-square width of the K layer are consistent with the limited available lidar record. The K data set is then used to investigate the impact of polar mesospheric clouds on the metal layers at high latitudes during summer. Finally, the occurrence frequency of sporadic K layers and their possible link to sporadic E layers are examined.
BibTeX:
@article{JGRD:JGRD52325,
  author = {Dawkins, E. C. M. and Plane, J. M. C. and Chipperfield, M. P. and Feng, W.},
  title = {The near-global mesospheric potassium layer: Observations and modeling},
  journal = {Journal of Geophysical Research: Atmospheres},
  year = {2015},
  volume = {120},
  number = {15},
  pages = {7975--7987},
  note = {2015JD023212},
  url = {http://dx.doi.org/10.1002/2015JD023212},
  doi = {10.1002/2015JD023212}
}
Raizada S, Tepley CA, Zhou Q, Sarkhel S, Mathews JD, Aponte N, Sekar I, Kerr R and Cabassa E (2015), "Dependence of mesospheric Na and Fe distributions on electron density at Arecibo", Earth Planets Space., September, 2015. Vol. 67(146)
Abstract: We present case studies of the mesospheric alkali and non-alkali metals, Na and Fe, along with electron concentrations [N e ] obtained from measurements made at Arecibo on nights of 17–18 and 18–19 March 2004. The background mesospheric conditions as recorded by an airglow all-sky imager displayed ripple- and band-type structures on these nights. Both of the metals display detailed structures within their neutral sporadic layer but are more pronounced in Na than for Fe. A sporadic-E (E s ) with electron concentrations [N e ] exceeding 3000 electrons cm ?3 is accompanied by a strong Na enhancement and a weak sporadic Fe (Fe s ) layer around 95-km altitude. The concentration of Fe + and Na + is estimated to be close to 600 and 30 ions.cm ?3 , respectively, within the sporadic-E layer. In order to investigate ion-neutral coupling, a correlative analysis was performed in two altitude regions. Similar features are seen between neutrals and electrons in the 96–100-km altitude range, while within the altitude range of 80–90 km, an opposite behavior is seen. A comparative study between neutral layers below 90 km often referred to as the main or permanent layer and sporadic activity above 90 km reveals different characteristics for alkali and non-alkali metal. Fe concentrations in the main layer are higher than in Fe s resulting in a density ratio of less than 1 determined from two layers of 3 km thickness centered at 97 and 87 km. For the case of Na, the ratio exceeds 1 during E s activity on both the nights.

The case studies discussed in this work facilitate our understanding of different factors that can influence the sporadic activity in alkali and non-alkali metals. In a region dominated by ion-molecule chemistry, temperature fluctuations that can be induced by wave activity will have more impact on Na than for Fe within their layers depending on altitude.

BibTeX:
@article{Raizada2015,
  author = {Shikha Raizada and Craig A Tepley and Qihou Zhou and Sumanta Sarkhel and John D Mathews and Nestor Aponte and Ilgin Sekar and Robert Kerr and Edvier Cabassa},
  title = {Dependence of mesospheric Na and Fe distributions on electron density at Arecibo},
  journal = {Earth Planets Space},
  year = {2015},
  volume = {67},
  number = {146},
  url = {http://www.earth-planets-space.com/content/67/1/146#abs},
  doi = {10.1186/s40623-015-0322-z}
}
Raizada S, Brum CM, Tepley CA, Lautenbach J, Friedman JS, Mathews JD, Djuth FT and Kerr C (2015), "First simultaneous measurements of Na and K thermospheric layers along with TILs from Arecibo", Geophysical Research Letters. Vol. 42(23), pp. 10,106-10,112.
Abstract: This work presents the first simultaneous observations of Na and K between 120 and 150 km altitudes along with ionospheric tidal ion layers (TILs) obtained on 30 January 2006 data from Arecibo. The latter displays an average downward phase velocity of ~14.7 ms-1. However, the neutral layers descend together at a much slower velocity of about ~0.69 ms-1. This indicates that thermospheric atomic metal layers are not necessarily associated with TILs. The ratio of the average Na/K abundances in thermosphere is ~35.5 as compared to 150 in the main layer (80–105 km). The long lifetimes of ions at ~140 km implies that neutral layers cannot result from direct neutralization of metal ions in the TILs. We investigate different mechanisms that can deposit neutral atoms at thermospheric altitudes.
BibTeX:
@article{Raizada2015b,
  author = {Raizada, Shikha and Brum, C. M. and Tepley, C. A. and Lautenbach, Jens and Friedman, J. S. and Mathews, John D. and Djuth, F. T. and Kerr, Caitlin},
  title = {First simultaneous measurements of Na and K thermospheric layers along with TILs from Arecibo},
  journal = {Geophysical Research Letters},
  year = {2015},
  volume = {42},
  number = {23},
  pages = {10,106--10,112},
  note = {2015GL066714},
  url = {http://dx.doi.org/10.1002/2015GL066714},
  doi = {10.1002/2015GL066714}
}
Sarkhel S, Mathews J, Raizada S, Sekar R, Chakrabarty D, Guharay A, Jee G, Kim J-H, Kerr R, Ramkumar G, Sridharan S, Wu Q, Mlynczak M and Russell JamesM I (2015), "A case study on occurrence of an unusual structure in the sodium layer over Gadanki, India", Earth, Planets and Space. Vol. 67(1) Springer Berlin Heidelberg.
Abstract: The height-time-concentration map of neutral sodium (Na) atoms measured by a Na lidar during the night of 18 to 19 March 2007 over Gadanki, India (13.5° N, 79.2° E) reveals an unusual structure in the Na layer for around 30 min in the altitude range of 92 to 98 km which is similar to the usual ‘C’ type structures observed at other locations. In order to understand the physical mechanism behind the generation of this unusual event, an investigation is carried out combining the data from multiple instruments that include the meteor wind radar over Thiruvananthapuram, India (8.5° N, 77° E) and the SABER instrument onboard the TIMED satellite. The temperature and wind profiles from the data set provided by these instruments allow us to infer the Richardson number which is found to be noticeably less than the canonical threshold of 0.25 above 92 km over Thiruvananthapuram suggesting the plausible generation of Kelvin-Helmholtz (KH) billows over southwestern part of the Indian subcontinent. Based on the average wind speed and direction over Thiruvananthapuram, it is proposed that the KH-billow structure was modified due to the background wind and was advected with it in nearly ‘frozen-in’ condition (without significant decay) in the northeastward direction reaching the Na lidar location (Gadanki). This case study, therefore, presents a scenario wherein the initially deformed KH-billow structure survived for a few hours (instead of a few minutes or tens of minutes as reported in earlier works) in an apparently ‘frozen-in’ condition under favorable background conditions. In this communication, we suggest a hypothesis where this deformed KH-billow structure plays crucial role in creating the abovementioned unusual structure observed in the Na layer over Gadanki.
BibTeX:
@article{Sarkhel2015,
  author = {Sarkhel, Sumanta and Mathews, JohnD and Raizada, Shikha and Sekar, Ramanathan and Chakrabarty, Dibyendu and Guharay, Amitava and Jee, Geonhwa and Kim, Jeong-Han and Kerr, RobertB and Ramkumar, Geetha and Sridharan, Sundararajan and Wu, Qian and Mlynczak, MartinG and Russell, JamesM, III},
  title = {A case study on occurrence of an unusual structure in the sodium layer over Gadanki, India},
  journal = {Earth, Planets and Space},
  publisher = {Springer Berlin Heidelberg},
  year = {2015},
  volume = {67},
  number = {1},
  url = {http://dx.doi.org/10.1186/s40623-015-0183-5},
  doi = {10.1186/s40623-015-0183-5}
}
Smith JA and Chu X (2015), "High-efficiency receiver architecture for resonance-fluorescence and Doppler lidars", Applied Optics., Apr, 2015. Vol. 54(11), pp. 3173-3184. OSA.
Abstract: A high-efficiency lidar receiver architecture that emphasizes boosting the receiver collection efficiency of resonance-fluorescence and Doppler lidars has opened up new avenues of study for the mesosphere and lower thermosphere-extended (MLT-X) at sites in Boulder, Colorado, USA, and Cerro Pach&xF3;n, Chile. Described in this work are in-depth considerations in the design, construction, and alignment of Na Doppler lidar receivers that have yielded signal levels typically 5&x2013;10 times higher per power-aperture product than any demonstrated in the literature, to these authors&x2019; knowledge, making studies of fine-scale MLT turbulence and tenuous thermospheric layers in Na possible with temperature and vertical wind capability for the first time. A lowering of the detection threshold by higher receiver collection efficiency at Cerro Pach&xF3;n has enabled this Na Doppler lidar to extend its measurement range far higher into the thermosphere, to regions with Na density less than 3&x2009;&x2009;cm&x2212;3. With renewed interest in the MLT-X region prompted by recent lidar discoveries of Fe in the thermosphere reaching 170&xA0;km at McMurdo, Antarctica, the receiver optimizations we have made now enable addressing an important need in the community. In addition, the higher spatial and temporal resolutions afforded by high signal-to-noise ratio, down to resolutions of &x223C;20&x2009;&x2009;s and &x223C;20&x2009;&x2009;m, promise to make the first direct measurements of eddy flux in the mesopause region possible. Results from deployment of optimized receivers at the Table Mountain Lidar Observatory in Boulder, the Andes Lidar Observatory at Cerro Pach&xF3;n, and the Arecibo Observatory in Puerto Rico are presented to demonstrate the power and portability of our methods that are readily applicable to other lidar varieties, including, but not limited to, the newly developed Fe Doppler lidar and recently upgraded K Doppler lidar.
BibTeX:
@article{Smith:15,
  author = {John A. Smith and Xinzhao Chu},
  title = {High-efficiency receiver architecture for resonance-fluorescence and Doppler lidars},
  journal = {Applied Optics},
  publisher = {OSA},
  year = {2015},
  volume = {54},
  number = {11},
  pages = {3173--3184},
  url = {http://ao.osa.org/abstract.cfm?URI=ao-54-11-3173},
  doi = {10.1364/AO.54.003173}
}
Stefanello M, Muella M, Amorim D, Machado C, Bageston J, Pimenta A, Martinis C, Sullivan C, Bittencourt J and Schuch N (2015), "OI 630.0 nm all-sky image observations of medium-scale traveling ionospheric disturbances at geomagnetic conjugate points", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 128, pp. 58 - 69.
Abstract: Abstract This paper presents a medium-scale traveling ionospheric disturbance (MSTID) occurrence detected through the OI 630.0 nm emission all-sky images, obtained by ground-based imaging systems installed at close geomagnetic conjugate locations: one at the Southern Space Observatory-SSO/CRS/INPE-MCTI, (29.4°S, 53.8°W), in Sao Martinho da Serra, RS, Brazil, and another at the Arecibo Observatory (18.3°N, 66.7°W), in Puerto Rico. The images obtained show the optical signature of MSTIDs (low intensity regions of 630.0 nm airglow emission), propagating simultaneously in both hemispheres, during geomagnetically quiet conditions (Kp<3). Observations using digital ionosonde installed at Falkland Islands (51.4°S, 57.5°W) and Ramey, Puerto Rico (18.5°N, 67.1°W) show an abrupt upward motion of the ionospheric F region plasma and the occurrence of frequency-type spread-F that could be related to the MSTIDs observed optically. Using Global Positioning System (GPS) receiver data, we also obtained the rate of the Total Electronic Content (TEC) change (ROT) for two geomagnetically conjugated sites-Santa Maria (29.7°S, 53.7°W) and Virgin Islands (17.7° N, 64.7°W). The analysis of TEC allows us to identify an irregular ionization in the F layer associated with the passage of an MSTID. The possible effects of the South America Magnetic Anomaly (SAMA) on the electrodynamic processes that control the inter-hemispheric coupling that give origin to the conjugate MSTIDs are highlighted and discussed.
BibTeX:
@article{Stefanello201558,
  author = {M.B. Stefanello and M.T.A.H. Muella and D.C.M. Amorim and C.S. Machado and J.V. Bageston and A.A. Pimenta and C. Martinis and C. Sullivan and J.A. Bittencourt and N.J. Schuch},
  title = {OI 630.0 nm all-sky image observations of medium-scale traveling ionospheric disturbances at geomagnetic conjugate points},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2015},
  volume = {128},
  pages = {58 - 69},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682615000607},
  doi = {10.1016/j.jastp.2015.03.012}
}
Lomidze L and Scherliess L (2015), "Estimation of thermospheric zonal and meridional winds using a Kalman filter technique", Space Weather. Vol. 13(11), pp. 747-760.
Abstract: Knowledge of the thermospheric neutral wind and its horizontal components is critical for an improved understanding of F region dynamics and morphology. However, to date their reliable estimation remains a challenge because of difficulties in both measurement and modeling. We present a new method to estimate the climatology of the zonal and meridional components of thermospheric neutral wind at low and middle latitudes using a Kalman filter technique. First, the climatology of the magnetic meridional wind is obtained by assimilating seasonal maps of F region ionosphere peak parameters (NmF2 and hmF2), obtained from Constellation Observing System for Meteorology, Ionosphere, and Climate radio occultation data, into the Global Assimilation of Ionospheric Measurements Full Physics (GAIM-FP) model. GAIM-FP provides the 3-D electron density throughout the ionosphere, together with the magnetic meridional wind. Next, the global zonal and meridional wind components are estimated using a newly developed Thermospheric Wind Assimilation Model (TWAM). TWAM combines magnetic meridional wind data obtained from GAIM-FP with a physics-based 3-D thermospheric neutral wind model using an implicit Kalman filter technique. Ionospheric drag and ion diffusion velocities, needed for the wind calculation, are also taken from GAIM-FP. The obtained wind velocities are in close agreement with measurements made by interferometers and with wind values from the Horizontal Wind Model 93 (HWM93) over Millstone Hill, Arecibo, and Arequipa during December and June solstices, and March equinox. In addition, it is shown that compared to HWM93 the winds from TWAM significantly improve the accuracy of the Ionosphere/Plasmasphere Model in reproducing the observed electron density variation over the Weddell Sea Anomaly.
BibTeX:
@article{SWE:SWE20287,
  author = {Lomidze, Levan and Scherliess, Ludger},
  title = {Estimation of thermospheric zonal and meridional winds using a Kalman filter technique},
  journal = {Space Weather},
  year = {2015},
  volume = {13},
  number = {11},
  pages = {747--760},
  url = {http://dx.doi.org/10.1002/2015SW001250},
  doi = {10.1002/2015SW001250}
}
Tsuda T, Shepherd M and Gopalswamy N (2015), "Advancing the understanding of the Sun--Earth interaction---the Climate and Weather of the Sun--Earth System (CAWSES) II program", Progress in Earth and Planetary Science. Vol. 2(1), pp. 1-18.
Abstract: The Scientific Committee on Solar--Terrestrial Physics (SCOSTEP) of the International Council for Science (ICSU) implemented an international collaborative program called Climate and Weather of the Sun--Earth System (CAWSES), which was active from 2004 to 2008; this was followed by the CAWSES II program during the period of 2009--2013. The CAWSES program was aimed at improving the understanding of the coupled solar--terrestrial system, with special emphasis placed on the short-term (weather) and long-term (climate) variability of solar activities and their effects on and responses of Geospace and Earth's environment. Following the successful implementation of CAWSES, the CAWSES II program pursued four fundamental questions addressing the way in which the coupled Sun--Earth system operates over time scales ranging from minutes to millennia, namely, (1) What are the solar influences on the Earth's climate? (2) How will Geospace respond to an altered climate? (3) How does short-term solar variability affect the Geospace environment? and (4) What is the Geospace response to variable inputs from the lower atmosphere? In addition to these four major tasks, the SCOSTEP and CAWSES promoted E-science and informatics activities including the creation of scientific databases and their effective utilization in solar--terrestrial physics research. Capacity building activities were also enhanced during CAWSES II, and this represented an important contribution of SCOSTEP to the world's solar--terrestrial physics community. This introductory paper provides an overview of CAWSES II activities and serves as a preface to the dedicated review papers summarizing the achievements of the program's four task groups (TGs) and the E-science component.
BibTeX:
@article{Tsuda2015,
  author = {Tsuda, Toshitaka
and Shepherd, Marianna
and Gopalswamy, Nat}, title = {Advancing the understanding of the Sun--Earth interaction---the Climate and Weather of the Sun--Earth System (CAWSES) II program}, journal = {Progress in Earth and Planetary Science}, year = {2015}, volume = {2}, number = {1}, pages = {1--18}, url = {http://dx.doi.org/10.1186/s40645-015-0059-0}, doi = {10.1186/s40645-015-0059-0} }
Xiong C, Lühr H, Ma S and Schlegel K (2015), "Validation of GRACE electron densities by incoherent scatter radar data and estimation of plasma scale height in the topside ionosphere", Advances in Space Research., August, 2015. Vol. 119(0), pp. 2048-2057.
Abstract: Abstract This paper presents an effort of using incoherent scatter radar data for validating electron density (Ne) measurements performed by the GRACE satellites from year 2002 to 2012. For adjusting the bias of GRACE Ne data, the observations at high latitudes from EISCAT at Tromsø and Svalbard, as well as two incoherent scatter radars (ISR) at mid- and low latitudes, Millstone Hill and Arecibo, are used. The adjusted GRACE Ne data are further compared with the observations from the four ISRs. For EISCAT observations at Tromsø and Svalbard the comparison results are quite consistent, yielding correlation coefficients as high as 0.92, and an average bias value of about 3e10 m?3 is obtained. For the radars at Millstone Hill and Arecibo the results show excellent agreement, yielding correlation coefficients as high as 0.97 and an average bias of 1e10 m?3. The scale factor of adjusted GRACE Ne data is lower by 1% and 5% compared to Millstone Hill and Arecibo readings, respectively. We consider these differences as within the uncertainty of radar measurements. Using the adjusted GRACE Ne as well as CHAMP observations during four periods of coplanar orbits between 2003 and 2008, the plasma scale heights of the topside ionosphere are determined and further compared with IRI model predictions. We find significantly larger scale heights in particular at middle and high latitudes than expected from IRI. Outstanding are the regions of the mid-latitude electron density trough.
BibTeX:
@article{Xiong2014,
  author = {Chao Xiong and Hermann Lühr and ShuYing Ma and Kristian Schlegel},
  title = {Validation of GRACE electron densities by incoherent scatter radar data and estimation of plasma scale height in the topside ionosphere},
  journal = {Advances in Space Research},
  year = {2015},
  volume = {119},
  number = {0},
  pages = {2048-2057},
  url = {http://www.sciencedirect.com/science/article/pii/S0273117714004785},
  doi = {10.1016/j.asr.2014.07.022}
}
Yamashita CS (2015), "LONG TERM VARIABILITY OF F2 LAYER IN THE SOUTH AMERICAN SECTOR (Variabilidade de longo periodo da camada F2 no setor sul-americano)". Thesis at: Instituto Nacional de Pesquisas Espaciais (INPE). Sao Jose dos Campos, 2015-08-25, 2015. , pp. 119.
Abstract: In this thesis, the long term variability of the peak of the ionosphere (F2 layer) at low-latitude and equatorial regions of the South American sector is studied. This work is based on foF2, hpF2 and hmF2 parameters obtained through the ionospheric sounding records of the sites from Cachoeira Paulista (22,67 S; 44,99 W) and Fortaleza (3,71 S; 38,54º W). Data during quiet geomagnetic conditions at 12 LT (Local Time) were studied. Empirical models were created based on the main forcing production of diurnal ion pairs, that is, variation in the incidence of solar radiation over the years. In order to perform this study, the variations in solar parameters over the past four solar cycles (since 1970) have been studied: the index number of sunspots, solar radio flux at 10.7 cm (F10.7) and extreme ultraviolet radiation in two bands (26-34 nm and 0.1-50 nm) measured by SOHO/SEM instrument. Results of the historical analysis of the solar radiation flux show that the EUV radiation was reduced by approximately 25% in the cycle # 24 compared to the cycle # 23. These results indicate a decreasing trend in the quantity of incident solar irradiance at the Earth's atmosphere, which would have implications for the production of ions by photoionization. Through the study of variation of ionospheric parameters (excluding the auto variation due to deposition of solar energy by radiation incidence) it was found that the amount of peak electrons of the ionosphere above Cachoeira Paulista (based on foF2 parameter) decreased approximately ~ -20% during the southern hemisphere winter and increased by around ~ 15% during the summer. Such behavior indicates the range of possible variation in height of the atomic oxygen over the years, and this variability is strongly modulated by the period of the year. For Fortaleza, it was noted that the parameter foF2 showed a positive trend between 13-24% for most of the year. The parameters hpf2, hmF2 showed a negative trend of ~ -11-14% in July, and a positive trend of ~ +10-18% in summer and equinoxes.
BibTeX:
@phdthesis{Yamashita:2015:VaLoPe,
  author = {Yamashita, Cristina Sayuri},
  title = {LONG TERM VARIABILITY OF F2 LAYER IN THE SOUTH AMERICAN SECTOR (Variabilidade de longo periodo da camada F2 no setor sul-americano)},
  school = {Instituto Nacional de Pesquisas Espaciais (INPE)},
  year = {2015},
  pages = {119},
  url = {http://urlib.net/sid.inpe.br/mtc-m21b/2015/08.24.19.06}
}
Franco E (2015), "Research Experience for Undergraduates Program, PROGRESS REPORT SUMMER 2015"
BibTeX:
@techreport{,
  author = {Eframir Franco},
  title = {Research Experience for Undergraduates Program, PROGRESS REPORT SUMMER 2015},
  year = {2015}
}
Bösinger T, Demekhov AG, Ermakova EN, Haldoupis C and Zhou Q (2014), "Pulsating nighttime magnetic background noise in the upper ULF band at low latitudes", Journal of Geophysical Research: Space Physics., May, 2014. Vol. 119(5), pp. 4109-4119.
Abstract: We model long-period (~2?h) irregular pulsations in the ellipticity of magnetic background noise (MBN) in the upper ULF band which were frequently observed during nighttime at a low-latitude site on the Island of Crete. It is shown that such pulsations cannot be reproduced in the calculations when using the ionosphere parameters from the statistical IRI (International Reference Ionosphere) model, while regular diurnal signatures of the ellipticity spectrum at sunset and sunrise are successfully reproduced. We apply the same approach to the location of the Arecibo incoherent scatter radar and show that using actually measured ionosphere profiles (up to a height of 400?km) instead of IRI profiles produces the ellipticity pulsations very similar to those observed at Crete. Comparison of model results with the calculated behavior of Alfvén mode refractive index allows us to conclude that the observed nighttime long-period irregular pulsations in the MBN ellipticity are caused by dynamic processes at the upper boundary of the ionospheric E-F valley which serves as a subionospheric Alfvén resonator. Irregular widening, shrinking, and/or deepening of the valley with time scales of 1 to 4?h affect the electrodynamical properties of this resonator and manifest themselves in the magnetic background noise properties.
BibTeX:
@article{Boesinger2014,
  author = {Bösinger, T. and Demekhov, A. G. and Ermakova, E. N. and Haldoupis, C. and Zhou, Q.},
  title = {Pulsating nighttime magnetic background noise in the upper ULF band at low latitudes},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2014},
  volume = {119},
  number = {5},
  pages = {4109--4119},
  url = {http://dx.doi.org/10.1002/2014JA019906},
  doi = {10.1002/2014JA019906}
}
Dawkins ECM, Plane JMC, Chipperfield MP, Feng W, Gumbel J, Hedin J, Höffner J and Friedman JS (2014), "First global observations of the mesospheric potassium layer", Geophysical Research Letters., August, 2014. Vol. 41(15), pp. 5653-5661.
Abstract: Metal species, produced by meteoric ablation, act as useful tracers of upper atmosphere dynamics and chemistry. Of these meteoric metals, K is an enigma: at extratropical latitudes, limited available lidar data show that the K layer displays a semiannual seasonal variability, rather than the annual pattern seen in other metals such as Na and Fe. Here we present the first near-global K retrieval, where K atom number density profiles are derived from dayglow measurements made by the Optical Spectrograph and Infrared Imager System spectrometer on board the Odin satellite. This robust retrieval produces density profiles with typical layer peak errors of ±15% and a 2?km vertical grid resolution. We demonstrate that these retrieved profiles compare well with available lidar data and show for the first time that the unusual semiannual behavior is near-global in extent. This new data set has wider applications for improving understanding of the K chemistry and of related upper atmosphere processes.
BibTeX:
@article{Dawkins2014a,
  author = {Dawkins, E. C. M. and Plane, J. M. C. and Chipperfield, M. P. and Feng, W. and Gumbel, J. and Hedin, J. and Höffner, J. and Friedman, J. S.},
  title = {First global observations of the mesospheric potassium layer},
  journal = {Geophysical Research Letters},
  year = {2014},
  volume = {41},
  number = {15},
  pages = {5653--5661},
  url = {http://dx.doi.org/10.1002/2014GL060801},
  doi = {10.1002/2014GL060801}
}
Deng Y, Huang Y, Wu Q, Noto J, Drob D and Kerr RB (2014), "Comparison of the neutral wind seasonal variation from midlatitude conjugate observations", Journal of Geophysical Research: Space Physics., April, 2014. Vol. 119(4), pp. 3029-3035.
Abstract: The seasonal variation of F region neutral wind from the midlatitude conjugate Fabry-Perot interferometer observations has been studied. The meridional wind at Palmer station (64°S,64°W) has a significant local time dependence with strong equatorward wind at midnight and polarward wind at dawn and dusk. The zonal wind switches from eastward to westward in the early morning section. From the June solstice (austral winter) to equinox, the maximum meridional wind increases from 90?m/s to 130?m/s, and the zonal wind switches direction at an earlier local time. The neutral winds from Palmer have been compared with those from the geomagnetic conjugate location, Millstone Hill (MH). At equinox, the local time variation of neutral wind shows a very good conjugacy between these two locations. But at June solstice, the similarity in the zonal wind becomes less clear. This seasonal dependence can be attributed to the seasonal variation of solar and geomagnetic forcings. The annual variation of daily average neutral wind from Palmer and MH has also been compared. The meridional wind shows a clear offset of season, and the magnitude at Palmer is averagely 40?m/s more equatorward than that at MH. The zonal wind is dominantly westward at Palmer and eastward at MH. The annual variation of neutral wind, especially the zonal component, is much less symmetric between the two sites than the local time variation. The empirical horizontal wind model shows a good agreement with the observations in both local time and annual variations.
BibTeX:
@article{Deng2014,
  author = {Deng, Yue and Huang, Yanshi and Wu, Qian and Noto, John and Drob, Douglas and Kerr, Robert B.},
  title = {Comparison of the neutral wind seasonal variation from midlatitude conjugate observations},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2014},
  volume = {119},
  number = {4},
  pages = {3029--3035},
  url = {http://dx.doi.org/10.1002/2013JA019716},
  doi = {10.1002/2013JA019716}
}
Hysell DL, Larsen MF and Sulzer MP (2014), "High time- and height-resolution neutral wind profile measurements across the mesosphere/lower thermosphere region using the Arecibo incoherent scatter radar", Journal of Geophysical Research: Space Physics., March, 2014. Vol. 119, pp. 2345-2358.
Abstract: A method for estimating the vector neutral wind profiles in the mesosphere and lower thermosphere (MLT) region of the upper atmosphere from Arecibo dual-beam incoherent scatter radar data is presented. The method yields continuous estimates of both the altitude-averaged F-region plasma drifts and all three components of the altitude-resolved neutral wind profiles in the MLT using data taken while the Arecibo feed system swings in azimuth. The problem is mixed determined, and its solution is not inherently unique. Second order Tikhonov regularization is used to find solutions consistent with the available data while being minimally structured, additional structure being unsupported by the data. The solution is found using the method of conjugate gradient least squares and sparse matrix mathematics. Example data acquired during an interval of midlatitude spread F are used to illustrate the method. The estimated wind profiles exhibit characteristics broadly consistent with gravity waves but are impulsive, with features that generally persist for less than one and a half wave periods.
BibTeX:
@article{Hysell2014,
  author = {Hysell, D. L. and Larsen, M. F. and Sulzer, M. P.},
  title = {High time- and height-resolution neutral wind profile measurements across the mesosphere/lower thermosphere region using the Arecibo incoherent scatter radar},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2014},
  volume = {119},
  pages = {2345-2358},
  url = {http://dx.doi.org/10.1002/2013JA019621},
  doi = {10.1002/2013JA019621}
}
Hickey DA, Martinis CR, Erickson PJ, Goncharenko LP, Meriwether JW, Mesquita R, Oliver WL and Wright A (2014), "New radar observations of temporal and spatial dynamics of the midnight temperature maximum at low latitude and midlatitude", Journal of Geophysical Research: Space Physics. Vol. 119(12), pp. 10,499-10,506.
Abstract: Presented here are several cases of midnight temperature maximum (MTM) observations using the Millstone Hill incoherent scatter radar (ISR) and Arecibo ISR. The MTM, a temperature enhancement in the upper atmosphere (at ~300?km altitude), is a poorly understood phenomenon as observations are sparse. An upward propagating terdiurnal tide and coupling between atmospheric regions may play a large part in the generation of the MTM, yet this phenomenon and its implications are not fully understood. Two nights (6 March 1989 and 12 July 1988) show clear cases of the MTM occurring between 30 and 34°N with amplitudes of ~100?K and at ~18°N with amplitudes of ~40?K. The MTMs occurred later at the higher latitude. Experiments in 2013 also show a clear MTM at 34° and 36°N from 250 to 350?km altitude. The ionospheric measurements presented here demonstrate a new application of a well-established technique to study atmospheric parameters and allow us to study the latitudinal extent of the MTM. The results provide evidence of the phenomenon occurring at latitudes and altitudes not previously sampled by radar techniques, showing that the MTM is not just an equatorial process, but one that can easily reach midlatitudes. Simultaneous measurements with a Fabry-Perot interferometer allow us to compare the neutral temperatures with the ion temperature. Overall, these are key observations that point to large-scale effects that can help constrain model outputs at different heights and latitudes.
BibTeX:
@article{JGRA:JGRA51497,
  author = {Hickey, Dustin A. and Martinis, Carlos R. and Erickson, Philip J. and Goncharenko, Larisa P. and Meriwether, John W. and Mesquita, Rafael and Oliver, William L. and Wright, Ashley},
  title = {New radar observations of temporal and spatial dynamics of the midnight temperature maximum at low latitude and midlatitude},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2014},
  volume = {119},
  number = {12},
  pages = {10,499--10,506},
  url = {http://dx.doi.org/10.1002/2014JA020719},
  doi = {10.1002/2014JA020719}
}
Liu X, Xu J, Zhang S, Jiang G, Zhou Q, Yuan W, Noto J and Kerr R (2014), "Thermospheric planetary wave-type oscillations observed by FPIs over Xinglong and Millstone Hill", Journal of Geophysical Research: Space Physics., August, 2014. Vol. 119(8), pp. 6891-6901.
Abstract: Three-year (2010–2013) observations of thermospheric winds (at ~250?km) by Fabry-Perot interferometers at Xinglong (XL, 40.2°N, 117.4°E) and Millstone Hill (MH, 42.6°N, 71.5°W) are used to study the climatology of atmospheric planetary wave-type oscillations (PWTOs) with periods of 4–19?days. We find that (1) these PWTOs occur more frequently in the months from May to October. They are consistent with the summertime preference of middle-latitude ionospheric electron density oscillations noted in other studies. (2) The month-to-month variations in PWTOs show phase changes between MH and XL, switching from antiphase to in phase when PWTO periods vary from short to long. (3) Typical PWTOs show annual and semiannual variations. The relative intensity of annual over semiannual components for PWTOs is different between XL and MH. (4) Magnetic storms and substorms have little influences on the annual and semiannual variations of the typical PWTO amplitudes. (5) Meridional wind PWTOs with typical periodicity bands around 5, 8, and 16?days appear to be correlated to both solar wind speed and Kp oscillations, suggesting a possible influence of the solar wind corotating interaction regions on neutral wind dynamics.
BibTeX:
@article{Liu2014,
  author = {Liu, Xiao and Xu, Jiyao and Zhang, Shunrong and Jiang, Guoying and Zhou, Qihou and Yuan, Wei and Noto, John and Kerr, Robert},
  title = {Thermospheric planetary wave-type oscillations observed by FPIs over Xinglong and Millstone Hill},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2014},
  volume = {119},
  number = {8},
  pages = {6891--6901},
  url = {http://dx.doi.org/10.1002/2014JA020043},
  doi = {10.1002/2014JA020043}
}
Nicolls MJ, Vadas SL, Aponte N and Sulzer MP (2014), "Horizontal parameters of daytime thermospheric gravity waves and E region neutral winds over Puerto Rico", Journal of Geophysical Research: Space Physics. Vol. 119(1), pp. 575-600.
Abstract: We report on the electron density perturbation amplitudes, periods (up to 60 min), horizontal and vertical wavelengths, phase speeds, and propagation directions of daytime traveling ionospheric disturbances (TIDs) from 115 to 300 km altitude using dual-beam experiments at the Arecibo Observatory (AO), Puerto Rico. As in previous studies, we find a near continuum of waves above the AO. While the TIDs propagate in nearly all directions except purely westward, we find that most propagate southward southeastward. We find that TID amplitudes increase nearly exponentially with increasing period, although with a much smaller slope for periods >30 min. TID amplitudes peak on the bottomside of the F region. Typical vertical wavelengths increase from less than 50 km at low altitudes to ~100–300 km. Horizontal wavelengths increase from ?70–100?km to ?150–500 km over the same altitude range. Median vertical wavelengths, horizontal wavelengths, and periods increase with altitude up to z~<225 km and are approximately constant at higher altitudes. Horizontal phase speeds are >100–150?m/s. We also measure the E region horizontal neutral winds and find that they peak at ?150 m/s near z?105?km in the middle of the day. Wave phase speeds are in general greater than these ambient winds. In addition, by tracing individual wave packets vertically in altitude, we find that a packet's vertical wavelength generally peaks near the altitude where its inferred ion velocity amplitude is maximum. The vertical wavelength generally decreases above this altitude, an observation that is consistent with gravity wave packet theory.
BibTeX:
@article{Nicolls2014,
  author = {Nicolls, Michael J. and Vadas, Sharon L. and Aponte, Nestor and Sulzer, Michael P.},
  title = {Horizontal parameters of daytime thermospheric gravity waves and E region neutral winds over Puerto Rico},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2014},
  volume = {119},
  number = {1},
  pages = {575--600},
  url = {http://dx.doi.org/10.1002/2013JA018988},
  doi = {10.1002/2013JA018988}
}
Sojka JJ, Jensen JB, David M, Schunk RW, Woods T, Eparvier F, Sulzer MP, Gonzalez SA and Eccles JV (2014), "Ionospheric model-observation comparisons: E layer at Arecibo Incorporation of SDO-EVE solar irradiances", Journal of Geophysical Research: Space Physics., May, 2014. Vol. 119(5), pp. 3844-3856. Wiley-Blackwell.
Abstract: This study evaluates how the new irradiance observations from the NASA Solar Dynamics Observatory (SDO) Extreme Ultraviolet Variability Experiment (EVE) can, with its high spectral resolution and 10?s cadence, improve the modeling of the E region. To demonstrate this a campaign combining EVE observations with that of the NSF Arecibo incoherent scatter radar (ISR) was conducted. The ISR provides E region electron density observations with high-altitude resolution, 300?m, and absolute densities using the plasma line technique. Two independent ionospheric models were used, the Utah State University Time-Dependent Ionospheric Model (TDIM) and Space Environment Corporation's Data-Driven D Region (DDDR) model. Each used the same EVE irradiance spectrum binned at 1?nm resolution from 0.1 to 106?nm. At the E region peak the modeled TDIM density is 20% lower and that of the DDDR is 6% higher than observed. These differences could correspond to a 36% lower (TDIM) and 12% higher (DDDR) production rate if the differences were entirely attributed to the solar irradiance source. The detailed profile shapes that included the E region altitude and that of the valley region were only qualitatively similar to observations. Differences on the order of a neutral-scale height were present. Neither model captured a distinct dawn to dusk tilt in the E region peak altitude. A model sensitivity study demonstrated how future improved spectral resolution of the 0.1 to 7?nm irradiance could account for some of these model shortcomings although other relevant processes are also poorly modeled.
BibTeX:
@article{Sojka2014a,
  author = {Sojka, Jan J. and Jensen, Joseph B. and David, Michael and Schunk, Robert W. and Woods, Tom and Eparvier, Frank and Sulzer, Michael P. and Gonzalez, Sixto A. and Eccles, J. Vincent},
  title = {Ionospheric model-observation comparisons: E layer at Arecibo Incorporation of SDO-EVE solar irradiances},
  journal = {Journal of Geophysical Research: Space Physics},
  publisher = {Wiley-Blackwell},
  year = {2014},
  volume = {119},
  number = {5},
  pages = {3844-3856},
  url = {http://dx.doi.org/10.1002/2013JA019528},
  doi = {10.1002/2013ja019528}
}
Venkatesh K, Rao PR and Fagundes PR (2014), "The role of altitudinal variation of scale height in determining the topside electron density profile over equatorial and low latitude sectors", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 121, Part A(0), pp. 72 - 82.
Abstract: Abstract Studies on the topside electron density profile variations have gained significant importance in the recent past in view of the trans-ionospheric communication and navigation applications particularly over the equatorial and low latitude sectors. The determination of scale height to be used in analytical functions has become more important in estimating the vertical electron density profile in the topside ionosphere. The incoherent scatter radar data over an equatorial station Jicamarca and a low latitude station Arecibo during the high solar activity years 2001 and 2002 are used to estimate the altitudinal dependence of topside ionospheric scale height. These scale height values at different altitudes are used to reconstruct the topside electron density profiles to study the changes in the shape of the topside profile due to the varying scale height values. It has been observed that a closer estimates of the electron density profiles in the topside ionosphere can be derived by using scale height values around 550&#xa0;km over Jicamarca and around 500&#xa0;km over Arecibo. The IRI-2012 modeled electron density profiles have been derived by giving F-layer peak density and height as inputs and those modeled profiles are compared with ISR measured and reconstructed profiles. Further, the scale height values in the topside ionosphere are computed using the IRI-2012 modeled electron and ion temperatures around 550&#xa0;km altitudes over Jicamarca and around 500&#xa0;km altitude over Arecibo. The scale height values thus derived have been used to reconstruct the topside electron density profiles over Jicamarca and Arecibo, the results of which have also been discussed in this paper.
BibTeX:
@article{Venkatesh201472,
  author = {K. Venkatesh and P.V.S. Rama Rao and Paulo R. Fagundes},
  title = {The role of altitudinal variation of scale height in determining the topside electron density profile over equatorial and low latitude sectors},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2014},
  volume = {121, Part A},
  number = {0},
  pages = {72 - 82},
  url = {http://www.sciencedirect.com/science/article/pii/S136468261400234X},
  doi = {10.1016/j.jastp.2014.10.006}
}
Wu Q, Noto J, Kerr R, Kapali S, Riccobono J, Wang W and Talaat ER (2014), "First Palmer and Millstone Hill midlatitude conjugate observation of thermospheric winds", Journal of Geophysical Research: Space Physics., April, 2014. Vol. 119(4), pp. 3016-3028.
Abstract: The first midlatitude conjugate thermospheric wind observations in the American sector showed various degrees of conjugacy between Palmer (64°S, 64°W, magnetic latitude (MLAT) 50°S) and Millstone Hill (42.82°N, 71.5°W, MLAT 53°N) under three different geomagnetic conditions (recovery after a substorm, moderately active, and quiet). The agreement with the National Center for Atmospheric Research's Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) simulations also varies with the geomagnetic activity level. During substorm recovery, the observations at Palmer (PA) and Millstone Hill (MH) both showed strong westward zonal winds, which the standard TIEGCM greatly underestimated. Inadequate ion convection pattern size and lack of effect from Subauroral Polarization Streams (SAPS) may be the cause of the large discrepancy. The TIEGCM with a SAPS model produced stronger westward zonal winds near PA but did not change the zonal wind near MH. The empirical SAPS model needs further refinements. In general, there is better conjugacy with moderate geomagnetic activity levels. The TIEGCM also agrees better with the observations. Under geomagnetically quiet conditions, the meridional winds appear to be less conjugate. The agreement between the observations and model is reasonable. Optical conjugate observations are severely limited by the seasons and weather conditions in the two hemispheres. Yet they are necessary to understanding the thermospheric dynamics in the subauroral region and its relationship with geomagnetic activity levels. The comparisons with TIEGCM are necessary for future model improvements.
BibTeX:
@article{Wu2014,
  author = {Wu, Qian and Noto, John and Kerr, Robert and Kapali, Sudha and Riccobono, Juanita and Wang, Wenbin and Talaat, Elsayed R.},
  title = {First Palmer and Millstone Hill midlatitude conjugate observation of thermospheric winds},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2014},
  volume = {119},
  number = {4},
  pages = {3016--3028},
  url = {http://dx.doi.org/10.1002/2013JA019062},
  doi = {10.1002/2013JA019062}
}
Aponte N, Brum CGM, Sulzer MP and Gonzalez SA (2013), "Measurements of the O+ to H+ transition height and ion temperatures in the lower topside ionosphere over Arecibo for equinox conditions during the 2008-2009 extreme Solar Minimum", Journal of Geophysical Research: Space Physics., July, 2013. Vol. 118, pp. 4465-4470.
Abstract: We present incoherent scatter radar measurements of electron density, electron and ion temperatures and ion composition made at Arecibo Observatory (18.35oN; 66.75oW), which is at a latitude 30oN geomagnetic (or 46.7o dip latitude) during the recent extreme solar minimum of 2007-2009 and find agreement between our data and recent reports of corresponding satellite observations. Both the in situ spacecraft measurements and our ground based radar profiles exhibit unusually low electron densities and cold temperatures. These 2 factors result in an extraordinarily contracted ionosphere and thermosphere. This contraction in the ionosphere in turn causes the O+/H+ transition height to descend, thus the base of the low latitude plasmasphere, or protonosphere, is found at extraordinary low altitudes. We show that during the geomagnetically quiet period of October 2009, the transition height ht, where [O+]=[H+]+[He+], was observed at altitudes as low as 800-820 km during the daytime, and descended as low as 450 km during the night. At night, when Te= Ti=Tn, temperatures below 675 K were measured at 03:00 Atlantic Standard Time (AST). These values are about 100K lower than corresponding temperatures observed by the Arecibo incoherent scatter radar during the previous solar minimum period (1995-1997).
BibTeX:
@article{Aponte2013,
  author = {Aponte, Néstor and Brum, Christiano G. M. and Sulzer, Michael P. and Gonzalez, Sixto A.},
  title = {Measurements of the O+ to H+ transition height and ion temperatures in the lower topside ionosphere over Arecibo for equinox conditions during the 2008-2009 extreme Solar Minimum},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2013},
  volume = {118},
  pages = {4465-4470},
  url = {http://dx.doi.org/10.1002/jgra.50416},
  doi = {10.1002/jgra.50416}
}
Chen T-J, Wu L-L, Liang J and Zhou QH (2013), "Research and Analysis on Ionospheric Composition Based on Particle Swarm Optimization", Intelligent Computing Theories and Technology - Lecture Notes in Computer Science. , pp. 596-604.
Abstract: A new analysis method for the molecular ion composition is proposed in this paper. The ionospheric data is measured by incoherent scattering radars (ISR). Contrast to the least square method fit (LSF), which is commonly used on ionospheric composition analyses, the particle swarm optimizer (PSO) is introduced to manipulate the data from ISR. The temperature-composition (TC) dependence problem by the LSF is revisited. The parameters of the Standard Particle Swarm Optimization algorithm (SPSO) for ionospheric composition analyses are determined. Experimental results show that PSO presents a better performance comparing with LSF and can be considered as a potential solution to solve ionospheric composition analysis problem.
BibTeX:
@article{Chen2013,
  author = {Tie-Jun Chen and Li-Li Wu and J.J. Liang and Qihou H. Zhou},
  title = {Research and Analysis on Ionospheric Composition Based on Particle Swarm Optimization},
  journal = {Intelligent Computing Theories and Technology - Lecture Notes in Computer Science},
  year = {2013},
  pages = {596-604},
  url = {http://dx.doi.org/10.1007/978-3-642-39482-9_69},
  doi = {10.1007/978-3-642-39482-9_69}
}
Lu G, Goncharenko LP, Coster AJ, Richmond AD, Roble RG, Aponte N and Paxton LJ (2013), "A Data-model Comparative Study of Ionospheric Positive Storm Phase in the Midlatitude F Region", In Midlatitude Ionospheric Dynamics and Disturbances. , pp. 63-75. American Geophysical Union.
Abstract: This chapter contains sections titled:

* Introduction

* Observations and Model Comparison

* Discussion

* Conclusion

BibTeX:
@inbook{eltit,
  author = {Lu, G. and Goncharenko, L. P. and Coster, A. J. and Richmond, A. D. and Roble, R. G. and Aponte, N. and Paxton, L. J.},
  title = {A Data-model Comparative Study of Ionospheric Positive Storm Phase in the Midlatitude F Region},
  booktitle = {Midlatitude Ionospheric Dynamics and Disturbances},
  publisher = {American Geophysical Union},
  year = {2013},
  pages = {63--75},
  url = {http://dx.doi.org/10.1029/181GM07},
  doi = {10.1029/181GM07}
}
Friedman JS, Chu X, Brum CGM and Lu X (2013), "Observation of a thermospheric descending layer of neutral K over Arecibo", Journal of Atmospheric and Solar-Terrestrial Physics., September, 2013. Vol. 104, pp. 253-259.
Abstract: We report on the first observation of a descending layer of atomic potassium (K) in the thermosphere. This observation was made with the K Doppler lidar at the Arecibo Observatory in Puerto Rico (18.35N; 66.75W) on 12 March 2005. The layer was first observed before 08:00 UT(04:00 AST) centered near 145km with the vertical extent up to about 155km, and then it descended to near 126km just over 2h later at dawn. The descent rate of 2.56+-0.38m/s matches the vertical phase speed of the GSWM09-computed semidiurnal tide between 120 and 150km. This also matches the descent rates of the thermospheric semidiurnal tides measured at Arecibo. Although the K density above 120km remains less than 1cm-3, its presence is unequivocal and has strong similarities to the neutral iron (Fe) layers in the thermosphere over 155km recently discovered by lidar observations at McMurdo, Antarctica. The thermospheric K layer is plausibly explained by radiative electron recombination with K+ within a tidal ion layer, which descends with the downward phase progression of the semidiurnal tide. Based on the production rate of K atoms and using current knowledge of tidal ion layer composition, we calculate an electron density of near 5×1e4cm-3 and K+ concentration of 650cm-3 at 135km immediately prior to the layer formation. This discovery of a thermospheric K layer, coupled with the McMurdo discovery of similar Fe layers, may lead to a new approach to studying the thermosphere in the altitude range of about 100-150km with resonance fluorescence lidars.
BibTeX:
@article{Friedman2013,
  author = {Jonathan S. Friedman and Xinzhao Chu and Christiano Garnett Marques Brum and Xian Lu},
  title = {Observation of a thermospheric descending layer of neutral K over Arecibo},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
  year = {2013},
  volume = {104},
  pages = {253-259},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682613000783},
  doi = {10.1016/j.jastp.2013.03.002}
}
Friedrich M and Fankhauser M (2013), "Time constants in the ionosphere from neural network models", Advances in Space Research. Vol. 51(4), pp. 691-695.
Abstract: Neural network (NN) models for the low latitude and the polar ionosphere from the D- to the F-region were developed which are based on incoherent scatter radar data from Arecibo and EISCAT Svalbard, respectively. The various geophysical input parameters defining the NN are not only the ones that represent the time one wants to predict, but also the geophysical conditions prior to the time of the prediction. The optimum length of these preceding periods are derived for the two models are different, but a period of 60 days is a compromise acceptable for both latitudes. Furthermore from the Arecibo data time constants of electron density decay after sundown are derived which – arguably – are also relevant elsewhere, including the polar latitudes. Whereas at all altitudes the electron densities decay exponentially after sundown, below 300 km there is an additional variation with solar zenith angle.
BibTeX:
@article{Friedrich2013,
  author = {Martin Friedrich and Martin Fankhauser},
  title = {Time constants in the ionosphere from neural network models},
  journal = {Advances in Space Research},
  year = {2013},
  volume = {51},
  number = {4},
  pages = {691-695},
  url = {http://dx.doi.org/10.1016/j.asr.2011.09.020},
  doi = {10.1016/j.asr.2011.09.020}
}
Goncharenko LP, Hsu VW, Brum CGM, Zhang S-R and Fentzke JT (2013), "Wave signatures in the midlatitude ionosphere during a sudden stratospheric warming of January 2010", Journal of Geophysical Research: Space Physics. Vol. 118(1), pp. 472-487.
Abstract: This paper presents a case study of the day-to-day variability in the midlatitude upper atmospheric ion temperature (around 200-400km) with a focus on variability resulting from meteorological forcing. The data are obtained by the Millstone Hill incoherent scatter radar (42.6N, 288.5E) on 18-31 January 2010, in coincidence with a major sudden stratospheric warming. We elucidate oscillations in ion temperature with both tidal periods (8h and 12h) and non-tidal periods (>24h) by analyzing residuals between the observed temperatures and those expected from an empirical model. We present the spatial-temporal development of periodicities in ion temperature and discuss to what degree these periodicities might be related to the sudden stratospheric warming event. The spectral location and temporal evolution of periodicities with 9.9-12.9h and 6.2-7.9h suggest that they are related to the semidiurnal (12h) and terdiurnal (8h) tides that are enhanced during the sudden stratospheric warming. Periodicities with 3-4d and 10-13d are likely related to Rossby waves with 4d and 10d periods, while the strong periodicity observed at 16-17h could result from the nonlinear interaction of the quasi 2d wave with the semidiurnal tide. As planetary waves are not expected to propagate to altitudes of 200–250km, these experimental results raise questions about the potential mechanisms of coupling between the lower and upper atmosphere.
BibTeX:
@article{Goncharenko2013,
  author = {Goncharenko, Larisa P. and Hsu, Vicki W. and Brum, Christiano Garnett Marques and Zhang, Shun-Rong and Fentzke, Jonathan T.},
  title = {Wave signatures in the midlatitude ionosphere during a sudden stratospheric warming of January 2010},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2013},
  volume = {118},
  number = {1},
  pages = {472-487},
  note = {Arecibo author},
  url = {http://dx.doi.org/10.1029/2012JA018251},
  doi = {10.1029/2012JA018251}
}
Gong Y, Zhou Q, Zhang SD, Aponte N, Sulzer M and González SA (2013), "The F region and topside ionosphere response to a strong geomagnetic storm at Arecibo", Journal of Geophysical Research: Space Physics. Vol. 118(8), pp. 5177-5183.
Abstract: We analyze the data derived from the Arecibo incoherent scatter radar measurements to investigate the response of the F region and topside ionosphere to a strong geomagnetic storm that occurred during the period of 5–6 August 2011. The meridional wind was extremely enhanced at the early stage of the storm. The peak velocity reached approximately 300?m/s at an altitude of 340?km, which is seldom seen at the Arecibo latitude. During the storm, the vertical ion drift caused by the meridional wind was positively correlated with that caused by the electric field, which is opposite to the quiet time relationship. The disturbed vertical ion drifts resulted in large ionospheric perturbations in the F and topside regions. Several collapses were observed in hmF2 during the storm night. NmF2 rapidly increased after the storm and then decreased around midnight. At an altitude of 610?km, the concentration of H+ and O+, and the ratio of H+ over electron density all exhibited large variations. The ratio of H+ over electron density changed from less than 10% to more than 80% in a matter of 2?hours in the morning of 6 August. One explanation for such a behavior is that vertical transport dominates over charge exchange late at night due to the lower concentration of O+.
BibTeX:
@article{Gong2013,
  author = {Gong, Yun and Zhou, Qihou and Zhang, Shao Dong and Aponte, Néstor and Sulzer, Michael and González, Sixto A.},
  title = {The F region and topside ionosphere response to a strong geomagnetic storm at Arecibo},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2013},
  volume = {118},
  number = {8},
  pages = {5177--5183},
  url = {http://dx.doi.org/10.1002/jgra.50502},
  doi = {10.1002/jgra.50502}
}
Gong Y, Zhou Q and Zhang S (2013), "Atmospheric tides in the low-latitude E and F regions and their responses to a sudden stratospheric warming event in January 2010", Journal of Geophysical Research: Space Physics. Vol. 118(12), pp. 7913-7927.
Abstract: An extensive analysis of atmospheric tides in the low-latitude thermosphere and their responses to a major sudden stratospheric warming (SSW) event (18–23 January 2010) is presented. The analysis is based on observational data from the Arecibo dual-beam incoherent scatter radar. Important findings of the present study are as follows. (1) The diurnal tide with an evanescent phase structure dominates the F region meridional wind field. The diurnal tide has a peak amplitude of 45 m/s occurring at about 245 km, and it is very stable throughout the nine consecutive days' observation. Below 114 km, the vertical structures of the diurnal tide in the meridional and zonal components are consistent, which resemble the classical solar S1, 1 tidal mode. (2) The F region semidiurnal tide is much weaker and has larger day-to-day variability than the diurnal tide. In the E region, the semidiurnal amplitudes in the meridional and zonal components grow continuously in the altitude ranges from 106 to 121 km and from 100 to 115 km, respectively. The vertical wavelength of the zonal component is estimated to be 45 km above 100 km, which is close to the solar S2, 4 and S2, 5 tidal modes. (3) The semidiurnal and terdiurnal tides respond strongly to the SSW while the impact that the SSW has on the diurnal tide in the meridional wind is limited. During the SSW event, the amplitudes of the semidiurnal and terdiurnal tides are enhanced in the F region but reduced in the upper E region.
BibTeX:
@article{Gong2013b,
  author = {Gong, Yun and Zhou, Qihou and Zhang, Shaodong},
  title = {Atmospheric tides in the low-latitude E and F regions and their responses to a sudden stratospheric warming event in January 2010},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2013},
  volume = {118},
  number = {12},
  pages = {7913--7927},
  url = {http://dx.doi.org/10.1002/2013JA019248},
  doi = {10.1002/2013JA019248}
}
Hysell D, Nossa E, Aveiro H, Larsen M, Munro J, Sulzer M and Gonzalez S (2013), "Fine structure in midlatitude sporadic E layers", Journal of Atmospheric and Solar-Terrestrial Physics. Vol. 103(0), pp. 16-23.
Abstract: Fine structure in midlatitude sporadic E layer patches or “clouds” is apparent in incoherent scatter observations from the Arecibo Radio Telescope. The fine structure is wavelike with predominant horizontal wavelengths as large as about 2–3 km. We attribute the structure to a drift wave instability operating in the collisional regime. A linear, local dispersion relation for the waves is described which predicts growth driven by polarization electric fields in the cloud. A numerical simulation produces wave growth and other features consistent with the dispersion relation, including finite parallel wavenumbers. The kilometric irregularities are thought to be the primary waves from which secondary, meter-scale waves in the layers can form.
BibTeX:
@article{Hysell2013,
  author = {D.L. Hysell and E. Nossa and H.C. Aveiro and M.F. Larsen and J. Munro and M.P. Sulzer and S.A. Gonzalez},
  title = {Fine structure in midlatitude sporadic E layers},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
  year = {2013},
  volume = {103},
  number = {0},
  pages = {16-23},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682612003033},
  doi = {10.1016/j.jastp.2012.12.005}
}
Lastovicka J (2013), "Trends in the upper atmosphere and ionosphere: Recent progress", Journal of Geophysical Research: Space Physics. Vol. 118(6), pp. 3924-3935.
Abstract: The upper atmosphere and embedded ionosphere respond to increasing concentration of greenhouse gases and other drivers of long-term changes and trends. In this paper, the progress reached in investigations of long-term trends in the upper atmosphere and mesosphere in the last 2?years is briefly summarized. First information appeared about trends in electron temperature (positive trend), thermospheric neutral wind (complex pattern), and total electron content (nonnegative trend). Some new information created partial apparent discrepancies, particularly in the case of ion temperature trends. The quantitative discrepancy between observation-based and model-based trends in mesospheric temperatures and in polar mesospheric clouds has largely been removed. The first observations of trends in CO2 concentration in the lower thermosphere suggest a way how to reduce the observation-model difference in the thermosphere and ionosphere. The scenario of trends in the upper atmosphere and ionosphere is now more complete than it was 2?years ago, but still some gaps and discrepancies occur for further investigations.
BibTeX:
@article{Lastovicka2013,
  author = {Lastovicka, Jan},
  title = {Trends in the upper atmosphere and ionosphere: Recent progress},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2013},
  volume = {118},
  number = {6},
  pages = {3924--3935},
  url = {http://dx.doi.org/10.1002/jgra.50341},
  doi = {10.1002/jgra.50341}
}
Marinov P, Zhang S and Kutiev I (2013), "Comparison of topside ionosphere scale height modeled by the Topside Sounder Model and incoherent scatter radar ionospheric model", Advances in Space Research., November, 2013. Vol. 52(0), pp. 1717-1725.
Abstract: Abstract The topside ionosphere scale height extracted from two empirical models are compared in the paper. The Topside Sounder Model (TSM) provides directly the scale height (HT), while the incoherent scatter radar ionospheric model (ISRIM) provides electron density profiles and its scale height (HR) is determined by the lowest gradient in the topside part of the profile. HT and HR are presented for 7 ISR locations along with their dependences on season, local time, solar flux F10.7, and geomagnetic index ap. Comparison reveals that HT values are systematically lower than respective HR values as the average offset for all 7 stations is 55&#xa0;km. For the midlatitude stations Arecibo, Shigaraki, and Millstone Hill this difference is reduced to 43&#xa0;km. The range of variations of HR is much larger than that of HT, as the HT range overlaps the lower part of the HR range. Dependences on ap, DoY and LT are much stronger in the ISRIM than in TSM. This results in much larger values of HR at higher ap. Diurnal amplitude of HR is much larger than that of HT, with large maximum of HR at night. The present comparison yields the conclusion that the ISR measurements provide steeper topside Ne profiles than that provided by the topside sounders.
BibTeX:
@article{Marinov2013a,
  author = {Pencho Marinov and Shunrong Zhang and Ivan Kutiev},
  title = {Comparison of topside ionosphere scale height modeled by the Topside Sounder Model and incoherent scatter radar ionospheric model},
  journal = {Advances in Space Research},
  year = {2013},
  volume = {52},
  number = {0},
  pages = {1717-1725},
  url = {http://www.sciencedirect.com/science/article/pii/S0273117713001440},
  doi = {10.1016/j.asr.2013.03.008}
}
Martinis C, Hickey D, Oliver W, Aponte N, Brum CGM, Akmaev R, Wright A and Miller C (2013), "The midnight temperature maximum from Arecibo incoherent scatter radar ion temperature measurements", Journal of Atmospheric and Solar-Terrestrial Physics ., October, 2013. Vol. 103, pp. 129-137.
Abstract: Abstract The midnight temperature maximum (MTM) is studied using ion temperature data from the incoherent scatter radar at the Arecibo Observatory (18.3N, 66.2W). The MTM is characterized by fitting the radar data with a function that takes into account diurnal, semidiurnal and terdiurnal components. Under the hypothesis that the MTM is related to the amplification of the terdiurnal wave, a Gaussian amplification window is included in the fitting to automatically determine the time of occurrence, temporal duration, and amplitude of the MTM observed. This study focused initially on altitudes near 300km, the typical height of MTM observations from Fabry Perot Interferometers (FPIs). Out of the 491 days available between 1967 and 2010 only 82 showed reliable temperature determination throughout the night at this typically bottomside altitude of often low density and sharp density gradient. The analysis was expanded to include 229 usable nights at heights close to 330km and 367km, where better conditions for temperature determination exist. Most of these nights showed an MTM with amplitudes between 20 and 150K and peak occurrence times during local summer months. The seasonal dependence of MTM parameters is also investigated and compared with previous experimental and modeling studies.
BibTeX:
@article{Martinis2013,
  author = {C. Martinis and D. Hickey and W. Oliver and N. Aponte and C. G. M. Brum and R. Akmaev and A. Wright and C. Miller},
  title = {The midnight temperature maximum from Arecibo incoherent scatter radar ion temperature measurements},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2013},
  volume = {103},
  pages = {129-137},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682613001442},
  doi = {10.1016/j.jastp.2013.04.014}
}
Mathews JD (2013), "A short history of geophysical radar at Arecibo Observatory", History of Geo- and Space Sciences. Vol. 4(1), pp. 19-33.
Abstract: As Arecibo Observatory (AO) approaches its 50th anniversary, it is appropriate to review the many radars and ionospheric heaters that have been deployed on or near the 305 m dish and to summarize some of the innovative radar-based geophysical research that has resulted. The reasons William E. (Bill) Gordon developed the 305 m Arecibo dish are well known but are briefly reviewed. The early and then more recent radar/feed designs are reviewed as geophysical uses of Arecibo have evolved and as the full potential of the dish and nearby facilities was and is being realized from HF through S-band frequencies. This history surely has some gaps and there are a few mysteries. The community is encouraged to fill these gaps and to help complete the history.
BibTeX:
@article{Mathews2013,
  author = {Mathews, J. D.},
  title = {A short history of geophysical radar at Arecibo Observatory},
  journal = {History of Geo- and Space Sciences},
  year = {2013},
  volume = {4},
  number = {1},
  pages = {19--33},
  url = {http://www.hist-geo-space-sci.net/4/19/2013/},
  doi = {10.5194/hgss-4-19-2013}
}
Pradipta R, Rooker L, Whitehurst L, Lee M, Ross L, Sulzer M, Gonzalez S, Tepley C, Aponte N, See B and Hu K (2013), "Whistler wave-induced ionospheric plasma turbulence: Source mechanisms and remote sensing ", Journal of Atmospheric and Solar-Terrestrial Physics. Vol. 103(0), pp. 169 - 175.
Abstract: Abstract We report a series of experiments conducted at Arecibo Observatory in the past, aimed at the investigation of 40.75&#xa0;kHz whistler wave interactions with ionospheric plasmas and the inner radiation belts at L=1.35. The whistler waves are launched from a Naval transmitter (code-named NAU) operating in Aguadilla, Puerto Rico at the frequency and power of 40.75&#xa0;kHz and 100&#xa0;kW, respectively. Arecibo radar, CADI, and optical instruments were used to monitor the background ionospheric conditions and detect the induced ionospheric plasma effects. Four-wave interaction processes produced by whistler waves in the ionosphere can excite lower hybrid waves, which can accelerate ionospheric electrons. Furthermore, whistler waves propagating into the magnetosphere can trigger precipitation of energetic electrons from the radiation belts. Radar and optical measurements can distinguish wave–wave and wave–particle interaction processes occurring at different altitudes. Electron acceleration by different mechanisms can be verified from the radar measurements of plasma lines. To facilitate the coupling of NAU-launched 40.75&#xa0;kHz whistler waves into the ionosphere, we can rely on naturally occurring spread F irregularities to serve as ionospheric ducts. We can also use HF wave-created ducts/artificial waveguides, as demonstrated in our earlier Arecibo experiments and recent Gakona experiments at HAARP. The newly constructed Arecibo HF heater will be employed in our future experiments, which can extend the study of whistler wave interactions with the ionosphere and the magnetosphere/radiation belts as well as the whistler wave conjugate propagation between Arecibo and Puerto Madryn, Argentina.
BibTeX:
@article{Pradipta2013169,
  author = {R. Pradipta and L.A. Rooker and L.N. Whitehurst and M.C. Lee and L.M. Ross and M.P. Sulzer and S. Gonzalez and C. Tepley and N. Aponte and B.Z. See and K.P. Hu},
  title = {Whistler wave-induced ionospheric plasma turbulence: Source mechanisms and remote sensing },
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
  year = {2013},
  volume = {103},
  number = {0},
  pages = {169 - 175},
  note = {Recent Advances in Equatorial, Low- and Mid-latitude Aeronomy },
  url = {http://www.sciencedirect.com/science/article/pii/S1364682613001405},
  doi = {10.1016/j.jastp.2013.04.010}
}
Rapp M, Strelnikova I, Li Q, Engler N and Teiser G (2013), "Charged Aerosol Effects on the Scattering of Radar Waves from the D-Region", Climate and Weather of the Sun-Earth System (CAWSES). Vol. 19, pp. 339-363.
Abstract: Charged aerosol particles are an important contributor to the D-region charge balance and affect the scattering of radar waves. Among these particles are meteoric smoke particles (MSP) which occur at all D-region altitudes and all seasons, and mesospheric ice particles whose occurrence is confined to altitudes of ~80–90 km at polar latitudes during summer. We argue that it is the modification of electron diffusion by the heavy charged aerosol particles which is the prime effect leading to clearly detectable signatures in both incoherent and coherent radar backscatter. In the case of incoherent scatter, it is shown that the presence of charged aerosol particles modifies the incoherent scatter spectrum. Corresponding observations with the EISCAT UHF radar and the Arecibo radar have been used to detect both MSP and ice particles at D-region altitudes and characterize their radii and number densities. In the case of coherent scatter, it is argued that the modified diffusion properties of the D-region electrons lead to small scale structures at the radar Bragg wavelength due to turbulent mixing in combination with a large Schmidt number. To test this theory, calibrated echo strengths of polar mesosphere summer echoes have been measured with the EISCAT radars at Tromsø (69°N) and Svalbard (78°N) and collocated 53 MHz radars, thus covering frequencies of 53 MHz, 224 MHz, 500 MHz, and 933 MHz. Importantly, the vast majority of these observations show excellent agreement with the corresponding theoretical predictions thus providing strong support for this theory. This theory was subsequently applied to the same data sets in order to derive ice particle radii. Corresponding results are in excellent agreement with independent data sets from satellite-borne and ground-based optical observations. Finally, some suggestions for future investigations are given.
BibTeX:
@article{Rapp2013,
  author = {Rapp, Markus and Strelnikova, Irina and Li, Qiang and Engler, Norbert and Teiser, Georg},
  title = {Charged Aerosol Effects on the Scattering of Radar Waves from the D-Region},
  journal = {Climate and Weather of the Sun-Earth System (CAWSES)},
  year = {2013},
  volume = {19},
  pages = {339-363},
  url = {http://dx.doi.org/10.1007/978-94-007-4348-9_19},
  doi = {10.1007/978-94-007-4348-9_19}
}
Shi JK, Wang Z, Torkar K, Friedrich M, Wang X, Liu C, Guan YB and Zhu GW (2013), "Ionospheric E-F valley observed by a sounding rocket at the low-latitude station Hainan", Annales Geophysicae. Vol. 31(8), pp. 1459-1462.
Abstract: According to the sounding rocket experiment conducted at Hainan ionospheric observatory (19.5° N, 109.1° E), a valley between the E layer and F layer in the ionospheric electron density profile is observed and presented. The sounding rocket was launched in the morning (06:15 LT) on 7 May 2011, and the observed electron density profile outside the valley agrees with the simultaneous observation by the DPS-4 digisonde at the same station. The width of the observed valley was about 42 km, the depth almost 50%, and the altitude of the electron density minimum 123.5 km. This is the first observation of the E–F valley in the low-latitude region in the East Asian sector. The results are also compared with models, and the physical mechanism of the observed valley is discussed in this paper.
BibTeX:
@article{Shi2013,
  author = {Shi, J. K. and Wang, Z. and Torkar, K. and Friedrich, M. and Wang, X. and Liu, C. and Guan, Y. B. and Zhu, G. W.},
  title = {Ionospheric E-F valley observed by a sounding rocket at the low-latitude station Hainan},
  journal = {Annales Geophysicae},
  year = {2013},
  volume = {31},
  number = {8},
  pages = {1459--1462},
  url = {http://www.ann-geophys.net/31/1459/2013/},
  doi = {10.5194/angeo-31-1459-2013}
}
Whitehurst LN, Lee MC and Pradipta R (2013), "Large plasma filaments and geomagnetic field fluctuations excited concomitantly by solar powered microwave transmissions", Physica Scripta. Vol. 2013(T155), pp. 014011.
Abstract: We investigate large-scale, filament-type of ionospheric plasma turbulence produced by a ground-based solar-powered microwave transmission system. It is shown that microwaves can interact with the ionosphere, primarily, in the E region. Electron collisions play key roles in the generation of large-scale fluctuations in ionospheric plasma density and geomagnetic fields via a thermal filamentation instability. The threshold wave field intensities are found to be of~1 V m -1 for the instability. Possible radar detection of microwave-induced ionospheric plasma effects is discussed and planned for our future Arecibo experiments in Puerto Rico.
BibTeX:
@article{Whitehurst2013,
  author = {L N Whitehurst and M C Lee and R Pradipta},
  title = {Large plasma filaments and geomagnetic field fluctuations excited concomitantly by solar powered microwave transmissions},
  journal = {Physica Scripta},
  year = {2013},
  volume = {2013},
  number = {T155},
  pages = {014011},
  url = {http://stacks.iop.org/1402-4896/2013/i=T155/a=014011},
  doi = {10.1088/0031-8949/2013/T155/014011}
}
Yue X, Zhou Q, Raizada S, Tepley C and Friedman J (2013), "Relationship between mesospheric Na and Fe layers from simultaneous and common-volume lidar observations at Arecibo", Journal of Geophysical Research: Atmospheres. Vol. 118(2), pp. 905-916.
Abstract: We compare the mesospheric Na and Fe layers by using simultaneous and common-volume lidar measurements made at the Arecibo Observatory (18.3°N, 66.75°W), Puerto Rico, in 2003. The temporal variations of the two species are highly correlated at practically all heights, although not always positively. Positive correlations occur in the bottom and top sides while negative correlation is observed in a relatively narrow region in the middle part. Chemical and dynamical effects are discussed to interpret this particular relationship between Na and Fe layers. It is shown that gas phase chemistry determines the structure of the Na and Fe layers after the metals are ablated from meteoroids entering the atmosphere. The observed region of negative correlation appears to be slightly lower than that of the expected region of negative correlation based on inert response to dynamics. It appears that such a difference may be due to temperature-dependent chemistry. Overall, the observed correlations between Na and Fe layers can be well explained by their responses to wave dynamics.
BibTeX:
@article{Yue2013,
  author = {Yue, Xianchang and Zhou, Qihou and Raizada, Shikha and Tepley, Craig and Friedman, Jonathan},
  title = {Relationship between mesospheric Na and Fe layers from simultaneous and common-volume lidar observations at Arecibo},
  journal = {Journal of Geophysical Research: Atmospheres},
  year = {2013},
  volume = {118},
  number = {2},
  pages = {905-916},
  url = {http://dx.doi.org/10.1002/jgrd.50148},
  doi = {10.1002/jgrd.50148}
}
Zawdie KA, Huba JD and Wu T-W (2013), "Modeling 3-D artificial ionospheric ducts", Journal of Geophysical Research: Space Physics. Vol. 118(11), pp. 7450-7457.
Abstract: The injection of powerful HF waves into the ionosphere leads to strong electron heating followed by a pressure perturbation, which can drive electrons along the field line to the conjugate side, creating what is known as an artificial duct. The electron temperature along the duct is above the ambient temperature; the electron density is depleted on the heating side and increased on the conjugate side. Duct formation due to HF heating has previously been studied using a modified version of SAMI2 (Sami2 is Another Model of the Ionosphere). We use a similarly modified version of SAMI3 to examine the effects of zonal E × B drifts on interhemispheric ducts created by heating over Arecibo. We found that the longitudinal E × B drifts, particularly those caused by the zonal neutral winds, significantly suppress the effects of HF heating on the conjugate side, reducing the temperature and density increases by about 90% and 75%, respectively.
BibTeX:
@article{Zawdie2013,
  author = {Zawdie, K. A. and Huba, J. D. and Wu, T.-W.},
  title = {Modeling 3-D artificial ionospheric ducts},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2013},
  volume = {118},
  number = {11},
  pages = {7450--7457},
  url = {http://dx.doi.org/10.1002/2013JA018823},
  doi = {10.1002/2013JA018823}
}
Aponte LARM-CL;RP;LMR;BS;MPS;CT;SAG;N (2013), "Forward Acceleration of Ionospheric Electrons by NAU 40.75-kHz Whistler Waves Over Arecibo", IEEE Transactions on Plasma Science., October 17, 2013.
Abstract: We discuss a new mechanism to explain the forward acceleration of ionospheric electrons by whistler waves. We suggest this mechanism to be the key process responsible for our reported enhanced plasma lines detected by the Arecibo 430 MHz radar. These plasma lines are characterized by the frequency-downshifted spectra with a bandwidth of ~ 12 kHz. The backscatter radar operation indicates that electrons were accelerated upward along the Earth's magnetic field by the up-going 40.75 kHz whistler waves, which were launched from the NAU transmitter. They covered a broad range of altitudes ( ~ 300 km) and lasted for a period of a few minutes. This mechanism leads to the energization of electrons of ~ 13 eV inferred from Arecibo experiments.
BibTeX:
@article{,
  author = {Lisa A. Rooker; Min-Chang Lee ; Rezy Pradipta ; Laura M. Ross ; Bozhi See ; Michael P. Sulzer ; Craig Tepley ; Sixto A. Gonzalez ; Nestor Aponte},
  title = {Forward Acceleration of Ionospheric Electrons by NAU 40.75-kHz Whistler Waves Over Arecibo},
  journal = {IEEE Transactions on Plasma Science},
  year = {2013}
}
Brum CGM, Tepley CA, Fentzke JT, Robles E, dos Santos PT and Gonzalez SA (2012), "Long-term changes in the thermospheric neutral winds over Arecibo: Climatology based on over three decades of Fabry-Perot observations", Journal of Geophysical Research: Space Physics. Vol. 117(A2), pp. A00H14 (16 pages).
Abstract: We present a study of the climatology of thermospheric neutral wind (TNW) meridional and zonal components measured with the 630.0 nm nightglow Fabry-Perot interferometer at the Arecibo Observatory from 1980 to 2010. We show and discuss the solar and geomagnetic dependencies as well as the long-term trend of the TNW components and their variation over time and season. A main result of this study was the detection of a substantial seasonal and local time dependence of the response of the TNW to solar and geomagnetic activity. In addition, we found that there is a long-term trend in the thermospheric neutral wind, which can be of a larger magnitude than the variation found in the seasonal, solar cycle, and geomagnetic activity influences. A major signature of this trend over the last 30 years was an increase in the meridional northward component up to 1.4 m/s/yr before midnight local time during the summer.
BibTeX:
@article{Brum2012,
  author = {Brum, Christiano Garnett Marques and Tepley, Craig A. and Fentzke, Jonathan T. and Robles, Eva and dos Santos, Pedrina Terra and Gonzalez, Sixto A.},
  title = {Long-term changes in the thermospheric neutral winds over Arecibo: Climatology based on over three decades of Fabry-Perot observations},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2012},
  volume = {117},
  number = {A2},
  pages = {A00H14 (16 pages)},
  url = {http://dx.doi.org/10.1029/2011JA016458},
  doi = {10.1029/2011JA016458}
}
Delgado R, Friedman JS, Fentzke JT, Raizada S, Tepley CA and Zhou Q (2012), "Sporadic metal atom and ion layers and their connection to chemistry and thermal structure in the mesopause region at Arecibo", Journal of Atmospheric and Solar-Terrestrial Physics. Vol. 74(0), pp. 11-23.
Abstract: We present an analysis of two separate and distinct sporadic layer events in the mesosphere and lower thermosphere region above the Arecibo Observatory. These layers were observed in both neutral K and ionic Ca+ with lidars, and in electron density with incoherent scatter radar. Temperature profiles were determined from the K lidar. One sporadic event was a high altitude layer, in which both atomic and ion sporadic layers were positioned above 100 km altitude. This represents a relatively common sporadic layer visible in both ions and neutrals at Arecibo. The other observation was less typical, with a lower altitude and more diffuse sporadic E layer, extending from below 90 km to above 95 km, which dissipated coincident with growth of a sporadic neutral K layer. We analyze these separate events using a temperature-dependent chemical model, which employs commonly accepted chemical processes. We find that the model successfully reproduces the high altitude layer of June 12–13, 2002. The result shows a temperature dependence related to the chemical lifetimes of the metallic constituents, and that the neutral layer would not have formed had the temperature profile matched that of the MSIS-90 model. Second, the temperature dependent chemistry model also reproduced K+ in close agreement with electron densities on June 14–15, 2002. However, the modeled neutrals do not agree well with the observation above 90 km, and it likely requires inclusion of dynamical forcing and advection. We speculate that model and observational deficiencies, primarily exclusion of dynamics such as advection and wave interactions, are the likely shortcomings in the failure to reproduce the observations.
BibTeX:
@article{Delgado2012,
  author = {Ruben Delgado and Jonathan S. Friedman and Jonathan T. Fentzke and Shikha Raizada and Craig A. Tepley and Qihou Zhou},
  title = {Sporadic metal atom and ion layers and their connection to chemistry and thermal structure in the mesopause region at Arecibo},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
  year = {2012},
  volume = {74},
  number = {0},
  pages = {11-23},
  url = {http://dx.doi.org/10.1016/j.jastp.2011.09.004},
  doi = {10.1016/j.jastp.2011.09.004}
}
Echer MS, Echer E, Rigozo N, Brum CGM, Nordemann D and Gonzalez W (2012), "On the relationship between global, hemispheric and latitudinal averaged air surface temperature (GISS time series) and solar activity ", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 74(0), pp. 87-93.
Abstract: The air surface temperature is a basic meteorological parameter and its variation is a primary measure of global, regional and local climate changes. In this work, the global, hemispheric and latitudinal averaged air surface temperature time series, obtained from the NASA/Goddard Institute for Space Studies (GISS), and the Sunspot Number (Rz) for the interval 1880-2005, are decomposed in frequency bands through wavelet multi-resolution analysis. We have found a very low correlation between global, hemispheric and latitudinal averaged air surface temperature and Rz in the 11yr solar cycle band (8-16 years) from about 1880 to about 1950. Afterwards the correlation is higher. A very significant correlation (R around 0.57 to 0.80) is found in the about 22 yr solar Hale cycle band (16-32 years) with lags from zero to four years between latitudinal averages air surface temperature and Rz. Therefore it seems that the 22yr magnetic field solar cycle might have a higher effect on Earth's climate than solar variations related to the 11yr sunspot cycle.
BibTeX:
@article{Echer2012,
  author = {M.P. Souza Echer and E. Echer and N.R. Rigozo and C. G. M. Brum and D.J.R. Nordemann and W.D Gonzalez},
  title = {On the relationship between global, hemispheric and latitudinal averaged air surface temperature (GISS time series) and solar activity },
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2012},
  volume = {74},
  number = {0},
  pages = {87-93},
  note = {Arecibo author},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682611002756},
  doi = {10.1016/j.jastp.2011.10.002}
}
Fentzke JT, Hsu V, Brum CGM, Strelnikova I, Rapp M and Nicolls M (2012), "D region meteoric smoke and neutral temperature retrieval using the poker flat incoherent scatter radar", Geophysical Research Letters. Vol. 39(21), pp. L21102 (6 pages).
Abstract: This brief note describes the first measurement of the microphysical properties and variability of meteoric smoke particles (MSPs) at high latitude using the Poker Flat ISR (65.1N, 147.5W). We present a novel technique for determining height resolved daytime D region neutral temperatures, which takes into account the presence of charged dust. We discuss the temporal/spatial variability and the relation to meteoric input observed and MSP microphysical properties in the polar mesopause region. The derived nanometer sized MSPs are consistent with size profiles derived previously using radar/rocket techniques and we note that our results imply a lack of heavy cluster ions below 85 km during the observing period. This provides a template for potential use at many other radar sites for the determination of microphysical properties of MSPs and day-time neutral temperature in the D region that show good general agreement with model and satellite temperature data during the observing period.
BibTeX:
@article{Fentzke2012,
  author = {Fentzke, J. T. and Hsu, V. and Brum, C. G. M. and Strelnikova, I. and Rapp, M. and Nicolls, M.},
  title = {D region meteoric smoke and neutral temperature retrieval using the poker flat incoherent scatter radar},
  journal = {Geophysical Research Letters},
  year = {2012},
  volume = {39},
  number = {21},
  pages = {L21102 (6 pages)},
  url = {http://dx.doi.org/10.1029/2012GL053841},
  doi = {10.1029/2012GL053841}
}
Friedman JS, Maldonado-Nieves D, Gonzalez I, Lautenbach J, Chu X, Smith JA and Huang W (2012), "High spectral resolution test and calibration of an ultra-narrowband Faraday anomalous dispersion optical filter for use in daytime mesospheric resonance Doppler lidar", Journal of Atmospheric and Solar-Terrestrial Physics., May, 2012. Vol. 80, pp. 187-194.
Abstract: We present a high-spectral-resolution test and calibration station for precision measurement of ultra-narrow bandwidth optical filters, and how this is used in the processing of daytime measurements from a resonance Doppler potassium lidar at Arecibo. The test station consists of Doppler-free saturation–absorption spectroscopy coupled with a small free-spectral-range Fabry–Perot etalon, which produces a precise measurement of the filter passband over a range of 20&#xa0;GHz (40&#xa0;pm) or more with a resolution of under 2&#xa0;MHz. This setup is used to measure the bandpass function of a Faraday anomalous dispersion optical filter with a band center at 770&#xa0;nm and full width at half maximum of about 3.64&#xa0;GHz (?7.2&#xa0;pm), which is the principal spectral filter in the Arecibo lidar. This bandpass function is then used to calibrate the Doppler-broadened returns from the K lidar. As the Faraday filter passband is narrow enough, the return lidar signals in both the resonance fluorescence and Rayleigh scattering are affected. We describe a calibration process to deconvolve the measured filter function from the return signals in order to achieve accurate temperature measurements. Our approach is demonstrated with actual lidar measurements.
BibTeX:
@article{Friedman2012,
  author = {Jonathan S. Friedman and Darlene Maldonado-Nieves and Israel Gonzalez and Jens Lautenbach and Xinzhao Chu and John A. Smith and Wentao Huang},
  title = {High spectral resolution test and calibration of an ultra-narrowband Faraday anomalous dispersion optical filter for use in daytime mesospheric resonance Doppler lidar},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
  year = {2012},
  volume = {80},
  pages = {187-194},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682612000314},
  doi = {10.1016/j.jastp.2012.01.017}
}
Gong Y, Zhou Q, Zhang S, Aponte N, Sulzer M and Gonzalez S (2012), "Midnight ionosphere collapse at Arecibo and its relationship to the neutral wind, electric field, and ambipolar diffusion", Journal of Geophysical Research: Space Physics. Vol. 117(A8), pp. n/a-n/a.
Abstract: We report the analysis of “midnight collapse,” a large drop in the F-layer peak height (HmF2) around midnight, observed at Arecibo during Jan. 14–22, 2010. During the nine nights of observations, the first four nights (Jan. 14–17) exhibited modest drops in HmF2 while the last five nights (Jan. 18–22) showed more severe drops. We examine the roles played by the meridional wind, electric field, and ambipolar diffusion in driving the vertical ion motion. The collapse process can be classified into three stages: preconditioning, initial descent, and sustained descent. Severe collapses occur when HmF2 is preconditioned high prior to the collapse. Ambipolar diffusion is most important during the initial descent. Neutral wind and electric field are responsible for sustaining the collapse. During Jan. 18–22, HmF2 was pushed high by the neutral wind before the collapse started. Neutral wind and electric field were in phase during the sustained severe collapses. The diurnal tide of the meridional wind provided the general condition for the collapses. The terdiurnal tide was most important to cause the difference between the two periods in our observation. Previous studies largely emphasized meridional wind being the dominant mechanism causing midnight collapse. Our study suggests that electric field and ambipolar diffusion also play an important role and the former can be the most dominant factor in some cases.
BibTeX:
@article{Gong2012,
  author = {Gong, Yun and Zhou, Qihou and Zhang, Shaodong and Aponte, Nestor and Sulzer, Michael and Gonzalez, Sixto},
  title = {Midnight ionosphere collapse at Arecibo and its relationship to the neutral wind, electric field, and ambipolar diffusion},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2012},
  volume = {117},
  number = {A8},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2012JA017530},
  doi = {10.1029/2012JA017530}
}
Haldoupis C (2012), "Midlatitude Sporadic E. A Typical Paradigm of Atmosphere-Ionosphere Coupling", Space Science Reviews. Vol. 168(1-4), pp. 441-461.
Abstract: This paper provides a comprehensive update on sporadic E layers that is placed in the context of atmosphere-ionosphere coupling, exemplified here by the fundamental windshear theory processes that govern sporadic E layer formation and variability. Some basics of windshear theory are provided first, followed by a summary of key experimental results, their interpretation and physical understanding. The emphasis is placed on the wind shear control of the diurnal and sub-diurnal variability and altitude descent of sporadic E layers and the key role behind these properties of the diurnal and semidiurnal tides. Furthermore, the paper summarizes recent observations that establish a role also for the planetary waves in sporadic E layer occurrence and long-term variability. The possible mechanisms behind this interaction are examined and evidence is presented which shows that planetary waves affect sporadic E layers indirectly though the amplitude modulation of tides at lower altitudes in the MLT region. Only a brief mention is made about gravity wave effects on sporadic E, which apparently exist but cannot be as crucial in layer forming as thought in the past. There is now enough evidence to suggest that mid- and low-latitude sporadic E is not as “sporadic” as the name implies but a regularly occurring ionospheric phenomenon. This may suggest that the sporadic E layer physics can be incorporated in large-scale atmosphere-ionosphere coupling models.
BibTeX:
@article{Haldoupis2012,
  author = {Haldoupis, Christos},
  title = {Midlatitude Sporadic E. A Typical Paradigm of Atmosphere-Ionosphere Coupling},
  journal = {Space Science Reviews},
  year = {2012},
  volume = {168},
  number = {1-4},
  pages = {441-461},
  doi = {10.1007/s11214-011-9786-8}
}
Huang C, Zhang S, Zhou Q, Yi F and Huang K (2012), "Atmospheric waves and their interactions in the thermospheric neutral wind as observed by the Arecibo incoherent scatter radar", Journal of Geophysical Research: Atmospheres. Vol. 117(D19), pp. n/a-n/a.
Abstract: Atmospheric waves and their interactions in the thermospheric neutral wind are studied based on Arecibo incoherent scatter radar observations. Our analysis suggests that the thermospheric atmosphere is usually disturbed by certain types of waves, including tides, gravity waves, and planetary waves, of which the diurnal tide is almost always the dominant disturbance. Strong interactions (defined as the coexistence of strong positive and negative correlations among the interacting waves) between the diurnal tide and gravity waves are frequently observed during the entire observation period. These strong interactions can persist for several days, although they are highly intermittent. Moreover, the sum and difference interactions between the diurnal tide and gravity waves always occur simultaneously and the energy exchange between the interacting waves is sometimes reversible. In addition to tide–gravity wave interactions, tide–planetary wave and tide–tide interactions are also found in our data. In tide–planetary wave interactions, the tidal oscillations are modulated at the interacting planetary wave periods. A combination of bispectral and correlation analyses verifies the occurrence of nonlinear interactions among different tidal components in the middle thermosphere. Moreover, during tide–tide interactions, the energy transfer trend changes very frequently, indicating that tidal energy is frequently redistributed among different tidal components. Generally, our study provides proof of strong tide–gravity wave, tide–planetary wave, and tide–tide interactions in the middle thermosphere, which has rarely been reported to date.
BibTeX:
@article{Huang2012,
  author = {Huang, Chunming and Zhang, Shaodong and Zhou, Qihou and Yi, Fan and Huang, Kaiming},
  title = {Atmospheric waves and their interactions in the thermospheric neutral wind as observed by the Arecibo incoherent scatter radar},
  journal = {Journal of Geophysical Research: Atmospheres},
  year = {2012},
  volume = {117},
  number = {D19},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2012JD018241},
  doi = {10.1029/2012JD018241}
}
Hysell DL, Nossa E, Larsen MF, Munro J, Smith S, Sulzer MP and Gonzalez SA (2012), "Dynamic instability in the lower thermosphere inferred from irregular sporadic E layers", Journal of Geophysical Research: Space Physics. Vol. 117(A8), pp. n/a-n/a.
Abstract: Simultaneous observations of an irregular sporadic Elayer from the Arecibo incoherent scatter radar and a coherent scatter radar located on St. Croix are presented. The layers exhibit periodic structuring which is attributed to shear instability in the neutral flow. Estimates of the time-varying vector neutral wind profiles in which the layer was embedded are analyzed and shown to be shear unstable in the Richardson number sense. In addition to the calculation of the Richardson number values, we present an eigenvalue analysis of the model of Miles (1961) and Howard (1961) for the observed wind profiles. The calculated eigenmodes have dominant Kelvin-Helmholtz modes for the estimated flow that are propagating to the southwest with phase speeds near 50 m/s and horizontal wavelengths between 10–15 km. The growth times for the waves would have been as little as about 1 min. These features are in reasonable agreement with the observed of Es-layer structure. The Miles-Howard model has been analyzed extensively in the past using both analytic and numerical techniques, but calculations of eigenmodes for the equations in a case with background winds that have turning and speed shear have not been carried out previously, as far as we know. The difficulties associated with the calculation are related to identifying the fastest growing modes among the large number of modes that satisfy the equations. The technique and the relationship of the solutions to the observed sporadicE layer wave structure are described.
BibTeX:
@article{Hysell2012,
  author = {Hysell, D. L. and Nossa, E. and Larsen, M. F. and Munro, J. and Smith, S. and Sulzer, M. P. and Gonzalez, S. A.},
  title = {Dynamic instability in the lower thermosphere inferred from irregular sporadic E layers},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2012},
  volume = {117},
  number = {A8},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2012JA017910},
  doi = {10.1029/2012JA017910}
}
England SL, Liu G, Zhou Q, Immel TJ, Kumar KK and Ramkumar G (2012), "On the signature of the quasi-3-day wave in the thermosphere during the January 2010 URSI World Day Campaign", Journal of Geophysical Research: Space Physics. Vol. 117(A6), pp. n/a-n/a.
Abstract: Ultra-fast Kelvin waves with periods of 3–5 days are important in the coupling of the lower atmosphere to the thermosphere and ionosphere. Here we focus on the observations and effects of a 3-day wave during January 2010. As this time period coincides with a stratospheric warming event, a coordinated set of observations with incoherent scatter radars are available. While there is no evidence that the occurrence of this 3-day wave is connected with this event, these observations offer an unprecedented glimpse of the thermospheric conditions during this period, including the first-ever detection of a 3-day wave with an incoherent scatter radar. Using a combination of ground- and space-based observations, we identify an eastward moving zonal wave number-one 3-day equatorial wave that is comprised of a Kelvin wave at the lowest latitudes and a Rossby-gravity wave at higher latitudes. In the equatorial region, the vertical wavelength is ?40 km and the wave peaks in amplitude around 95–100 km altitude. The wave observed here is only seen to propagate to around 105 km altitude. Evidence of an interaction between this wave and the diurnal tide is seen between 82–88 km. The resultant 3-day periodicity in the diurnal tide is seen to propagate up to altitudes of ?150 km. This could have a significant impact on the ionosphere via modulation of the E-region dynamo, thus carrying the 3-day periodicity to higher altitudes.
BibTeX:
@article{JGRA:JGRA21902,
  author = {England, Scott L. and Liu, Guiping and Zhou, Qihou and Immel, Thomas J. and Kumar, Karanam K. and Ramkumar, Geetha},
  title = {On the signature of the quasi-3-day wave in the thermosphere during the January 2010 URSI World Day Campaign},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2012},
  volume = {117},
  number = {A6},
  pages = {n/a--n/a},
  url = {http://dx.doi.org/10.1029/2012JA017558},
  doi = {10.1029/2012JA017558}
}
Makela J and Otsuka Y (2012), "Overview of Nighttime Ionospheric Instabilities at Low- and Mid-Latitudes: Coupling Aspects Resulting in Structuring at the Mesoscale", Space Science Reviews. Vol. 168(1-4), pp. 419-440.
Abstract: We present a review of the current state of understanding regarding two classes of irregularities causing mesoscale structuring (hundreds of kilometers) in the nighttime ionosphere at low- and mid-latitudes. Additionally, current state of understanding of equatorial plasma bubbles at low latitudes, and medium-scale traveling ionospheric disturbances at mid latitudes and their relationship to possible seeding from lower altitudes are described. In each case, well-developed linear theories exist to explain the general properties of the irregularities. However, these linear theories have growth rates too low to explain the actual observations, giving rise to the need to invoke seeding mechanisms. We describe the observational databases that have been compiled over the decades and discuss possible coupling and seeding mechanisms that would overcome the low growth rate and explain the observed structuring at the mesoscale. Future research directions are also briefly discussed.
BibTeX:
@article{Makela2012,
  author = {Makela, JonathanJ. and Otsuka, Yuichi},
  title = {Overview of Nighttime Ionospheric Instabilities at Low- and Mid-Latitudes: Coupling Aspects Resulting in Structuring at the Mesoscale},
  journal = {Space Science Reviews},
  year = {2012},
  volume = {168},
  number = {1-4},
  pages = {419-440},
  doi = {10.1007/s11214-011-9816-6}
}
Nikoukar R, Kamalabadi F, Kudeki E and Sulzer M (2012), "On resolution/error trade-offs in incoherent scatter radar measurements", Radio Science. Vol. 47(1), pp. n/a-n/a.
Abstract: In this work, we investigate the performance of amplitude modulated coding schemes in incoherent scatter radar (ISR) measurements in terms of statistical estimation error, range resolution, and signal-to-noise ratio. We approach this goal by formulating the inherent trade-off between estimation error and resolution as mathematical measures for model order selection. These trade-offs are examined on numerical experiments with several amplitude modulated waveforms with different duty cycles. We demonstrate that compared with an unmodulated long pulse, reduced statistical estimation error with similar range resolution, or finer range resolution with similar estimation accuracy can be obtained by incorporating coding schemes.
BibTeX:
@article{Nikoukar2012,
  author = {Nikoukar, Romina and Kamalabadi, Farzad and Kudeki, Erhan and Sulzer, Michael},
  title = {On resolution/error trade-offs in incoherent scatter radar measurements},
  journal = {Radio Science},
  year = {2012},
  volume = {47},
  number = {1},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2011RS004685},
  doi = {10.1029/2011RS004685}
}
Pavlov A (2012), "Ion Chemistry of the Ionosphere at E- and F-Region Altitudes: A Review", Surveys in Geophysics. Vol. 33(5), pp. 1133-1172.
Abstract: The current state of knowledge of E- and F-region ion chemistry is reviewed. Considerable attention is given to the progress in the chemistry of unexcited N2+, O2+, NO+, O+(4S), N+, H+, He+, Fe+, Mg+, Na+, Ca+, and K+ ions and electronically excited O+(2D), O+(2P), O+(4P), and O+(2P*) ions. Achievements in our understanding of the role of vibrationally excited N2+, O2+, and NO+ ions in the ionosphere are discussed.
BibTeX:
@article{Pavlov2012,
  author = {Pavlov, A.V.},
  title = {Ion Chemistry of the Ionosphere at E- and F-Region Altitudes: A Review},
  journal = {Surveys in Geophysics},
  year = {2012},
  volume = {33},
  number = {5},
  pages = {1133-1172},
  url = {http://dx.doi.org/10.1007/s10712-012-9189-8},
  doi = {10.1007/s10712-012-9189-8}
}
Pfaff RF (2012), "The Near-Earth Plasma Environment", Space Science Reviews. Vol. 168(1-4), pp. 23- 112.
Abstract: An overview of the plasma environment near the earth is provided. We describe how the near-earth plasma is formed, including photo-ionization from solar photons and impact ionization at high latitudes from energetic particles. We review the fundamental characteristics of the earth’s plasma environment, with emphasis on the ionosphere and its interactions with the extended neutral atmosphere. Important processes that control ionospheric physics at low, middle, and high latitudes are discussed. The general dynamics and morphology of the ionized gas at mid- and low-latitudes are described including electrodynamic contributions from wind-driven dynamos, tides, and planetary-scale waves. The unique properties of the near-earth plasma and its associated currents at high latitudes are shown to depend on precipitating auroral charged particles and strong electric fields which map earthward from the magnetosphere. The upper atmosphere is shown to have profound effects on the transfer of energy and momentum between the high-latitude plasma and the neutral constituents. The article concludes with a discussion of how the near-earth plasma responds to magnetic storms associated with solar disturbances.
BibTeX:
@article{Pfaff2012,
  author = {Robert F. Pfaff},
  title = {The Near-Earth Plasma Environment},
  journal = {Space Science Reviews},
  year = {2012},
  volume = {168},
  number = {1-4},
  pages = {23- 112},
  doi = {10.1007/s11214-012-9872-6}
}
Raizada S, Tepley CA, Williams BP and Garcia R (2012), "Summer to winter variability in mesospheric calcium ion distribution and its dependence on Sporadic E at Arecibo", Journal of Geophysical Research: Space Physics. Vol. 117(A2), pp. n/a-n/a.
Abstract: We present a new investigation of the variability in the metallic calcium ion concentration near the mesopause region, and its relation to the electron concentration during summer and winter seasons at the Arecibo Observatory. During the summer months the ion layer is broader, extending to 87-88 km compared with winter months where it occurs above this altitude around midnight. The concentration maximizes to ~200 ions cm-3 around 90-95 km close to midnight during the summer. However, for the winter months, the peak occurs during the early morning hours in thin descending layers above 98 km. Summer to winter variation in the calcium ion to electron ratio displays an average value of ~0.15 and 0.05 during these seasons, respectively. A good correlation between them suggests that Ca+ densities are directly related to the strength of the Sporadic E, which is stronger in the summer. The average abundance of ions is 5.7 × 107 cm-2 and 4.6 × 107 cm-2 during summer and winter months respectively, while that for electrons is 1.2 × 1010 ions cm-2 and 5.8 × 1e9 ion cm-2 for these seasons. Both Ca+ and Ne display strong descending layers at different altitudes during summer and winter. Calcium ion lifetimes against neutralization are a factor of two lower during the summer than in the winter months around 90 km but similar at altitudes exceeding 95 km.
BibTeX:
@article{Raizada2012,
  author = {Raizada, Shikha and Tepley, Craig A. and Williams, Bifford P. and Garcia, Raul},
  title = {Summer to winter variability in mesospheric calcium ion distribution and its dependence on Sporadic E at Arecibo},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2012},
  volume = {117},
  number = {A2},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2011JA016953},
  doi = {10.1029/2011JA016953}
}
Sarkhel S, Raizada S, Mathews JD, Smith S, Tepley CA, Rivera FJ and Gonzalez SA (2012), "Identification of large-scale billow-like structure in the neutral sodium layer over Arecibo", Journal of Geophysical Research: Space Physics. Vol. 117(A10), pp. n/a-n/a.
Abstract: We present a rare event that was recorded over Arecibo using sodium (Na) lidar. Billow-like structures with periods of ~60 min were seen in the Na layer above 102 km on the night of 7–8 July 2010. The absence of any high-altitude structure was noted on the following night. Spectral analysis using the Lomb-Scargle technique reveals periods with larger power on the first night as compared to the adjacent one. The keograms derived from a sequence of 557.7 nm airglow images show the passage of a large frontal wave on 7–8 July 2010. Further investigation on the occurrence of neutral instabilities was carried out using mesospheric temperature and horizontal wind obtained from the Sounding of Atmosphere using Broadband Emission Radiometry (SABER) and TIMED Doppler Interferometer (TIDI) instruments onboard the TIMED satellite. A good agreement is observed between the temperatures derived from SABER and ground-based airglow instruments. The mesospheric temperature and horizontal wind profiles allowed the determination of square of the Brunt-Väisälä frequency and Richardson number to quantitatively evaluate the possible role of different instabilities in generating this structure. The profile of the former entity reveals that the region is convectively stable during the time when the event was observed. However, the presence of strong shears in the region, where billow-like structures are observed on 7–8 July 2010, is noted along with a Richardson number of 0.22, indicating the likely occurrence of dynamical instability. Thus, the present work suggests that dynamical instability make conditions conducive for billow-like structures in the Na layer above 102 km. The possible role of plasma processes in generating these structures is also discussed.
BibTeX:
@article{Sarkhel2012a,
  author = {Sarkhel, S. and Raizada, Shikha and Mathews, John D. and Smith, Steve and Tepley, Craig A. and Rivera, Francisco J. and Gonzalez, Sixto A.},
  title = {Identification of large-scale billow-like structure in the neutral sodium layer over Arecibo},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2012},
  volume = {117},
  number = {A10},
  pages = {n/a--n/a},
  url = {http://dx.doi.org/10.1029/2012JA017891},
  doi = {10.1029/2012JA017891}
}
Taori A, Raizada S, Ratnam MV, Tepley CA, Nath D and Jayaraman A (2012), "Role of Tropical Convective Cells in the Observed Middle Atmospheric Gravity Wave Properties from Two Distant Low Latitude Stations", Earth Science Research. Vol. 1, pp. 87-97.
Abstract: We investigate the role of convective processes in triggering middle atmospheric gravity waves with the help of simultaneous measurements of middle atmospheric temperature variability from two tropical stations, Gadanki (13.5oN, 79.2oE) and Arecibo (18.3oN, 66.7oW). Our data reveal that some of the wave periods are similar at both locations indicating the source regions of waves to be similar at both the stations. However, the potential energies of short period gravity waves are found to be significantly higher over Gadanki compared to that at Arecibo. The most striking observation is that background wind conditions were similar and convective processes occurred very close to Gadanki compared to Arecibo. In the view absence of other wave sources during the period of observations, we suggest the strength as well as the distance of convective cells from the location of the observations is responsible for the observed differences in gravity wave spectrum and energies.
BibTeX:
@article{Taori2012,
  author = {A. Taori and S. Raizada and M. Venkat Ratnam and C. A. Tepley and D. Nath and A. Jayaraman},
  title = {Role of Tropical Convective Cells in the Observed Middle Atmospheric Gravity Wave Properties from Two Distant Low Latitude Stations},
  journal = {Earth Science Research},
  year = {2012},
  volume = {1},
  pages = {87-97},
  doi = {10.5539/esr.v1n1p87}
}
Wu T-W, Huba JD, Joyce G and Bernhardt PA (2012), "Modeling Arecibo conjugate heating effects with SAMI2", Geophysical Research Letters. Vol. 39(7), pp. L07103 (5 pages).
Abstract: Conjugate heating effects associated with the upcoming Arecibo heater facility are studied using the NRL ionosphere model SAMI2. A density-dependent, localized heating source is included in the electron temperature equation to model ionospheric radiowave heating. Heating effects are examined as a function of the heating timing and the peak density of the unmodified ionosphere (through the F10.7 index). The simulation results suggest that field-aligned duct formation occur during periods of relatively low electron densities (e.g., during the night). The enhancement of the electron temperature and electron density in the conjugate topside ionosphere (~500 km) could reach respective values of ~5% and 25%. Heating losses associated with inelastic electron-neutral (N2) collisions primarily inhibit conjugate effects.
BibTeX:
@article{Wu2012,
  author = {Wu, T.-W. and Huba, J. D. and Joyce, G. and Bernhardt, P. A.},
  title = {Modeling Arecibo conjugate heating effects with SAMI2},
  journal = {Geophysical Research Letters},
  year = {2012},
  volume = {39},
  number = {7},
  pages = {L07103 (5 pages)},
  url = {http://dx.doi.org/10.1029/2012GL051311},
  doi = {10.1029/2012GL051311}
}
Brum CGM, Rodrigues FdS, dos Santos PT, Matta AC, Aponte N, Gonzalez SA and Robles E (2011), "A modeling study of foF2 and hmF2 parameters measured by the Arecibo incoherent scatter radar and comparison with IRI model predictions for solar cycles 21, 22, and 23", Journal of Geophysical Research: Space Physics. Vol. 116(A3), pp. n/a-n/a.
Abstract: This work presents the results of a local empirical model that describes the behavior of the ionospheric F2 region peak. The model was developed using nearly 25 years of incoherent scatter radar (ISR) measurements made at the Arecibo Observatory (AO) between 1985 and 2009. The model describes the variability of the F2 peak frequency (foF2) and F2 peak height (hmF2) as a function of local time, season, and solar activity for quiet-to-moderate geomagnetic activity conditions (Kp < 4+). Our results show that the solar activity control of hmF2 and foF2 over Arecibo can be better described by a new proxy of the solar flux (F107P), which is presented here. The variation of hmF2 parameter with F107P is virtually linear, and only a small saturation of the foF2 parameter is observed at the highest levels of solar flux. The winter anomaly and asymmetries in the variation of the modeled parameters between equinoxes were detected during the analyses and have been taken into account by the AO model. Comparisons of ISR data with international reference ionosphere (IRI) model predictions indicate that both CCIR and URSI modes overestimate foF2 during the daytime and underestimate it at night. As expected, this underestimation is not observed in the AO model. Our analyses also show that the hmF2 parameter predicted by the IRI modes shows a saturation point, which causes hmF2 to be underestimated at high solar activity. The underestimation increases with higher levels of solar activity. Finally, we also found that IRI predictions of the seasonal variability of foF2 and hmF2 over Arecibo can be improved by using a small correction that varies with solar activity and local time.
BibTeX:
@article{Brum2011,
  author = {Brum, Christiano Garnett Marques and Rodrigues, Fabiano da Silveira and dos Santos, Pedrina Terra and Matta, Aleshka Carrion and Aponte, Nestor and Gonzalez, Sixto A. and Robles, Eva},
  title = {A modeling study of foF2 and hmF2 parameters measured by the Arecibo incoherent scatter radar and comparison with IRI model predictions for solar cycles 21, 22, and 23},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2011},
  volume = {116},
  number = {A3},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2010JA015727},
  doi = {10.1029/2010JA015727}
}
Chau J, Goncharenko L, Fejer B and Liu H-L (2011), "Equatorial and Low Latitude Ionospheric Effects During Sudden Stratospheric Warming Events", Space Science Reviews. Vol. 168, pp. 385-417.
Abstract: There are several external sources of ionospheric forcing, including these are solar wind-magnetospheric processes and lower atmospheric winds and waves. In this work we review the observed ion-neutral coupling effects at equatorial and low latitudes during large meteorological events called sudden stratospheric warming (SSW). Research in this direction has been accelerated in recent years mainly due to: (1) extensive observing campaigns, and (2) solar minimum conditions. The former has been instrumental to capture the events before, during, and after the peak SSW temperatures and wind perturbations. The latter has permitted a reduced forcing contribution from solar wind-magnetospheric processes. The main ionospheric effects are clearly observed in the zonal electric fields (or vertical E×B drifts), total electron content, and electron and neutral densities. We include results from different ground- and satellite-based observations, covering different longitudes and years. We also present and discuss the modeling efforts that support most of the observations. Given that SSW can be forecasted with a few days in advance, there is potential for using the connection with the ionosphere for forecasting the occurrence and evolution of electrodynamic perturbations at low latitudes, and sometimes also mid latitudes, during arctic winter warmings.
BibTeX:
@article{Chau2012,
  author = {Chau, JorgeL. and Goncharenko, LarisaP. and Fejer, BelaG. and Liu, Han-Li},
  title = {Equatorial and Low Latitude Ionospheric Effects During Sudden Stratospheric Warming Events},
  journal = {Space Science Reviews},
  year = {2011},
  volume = {168},
  pages = {385-417},
  doi = {10.1007/s11214-011-9797-5}
}
Cohen MH and Lane NF (2011), "William Edwin Gordon 1918-2010", NAS Biographical Memoir. Vol. n/a-n/a, pp. 22 pages. National Academy of Sciences.
Abstract: William Edwin Gordon was born in Patterson, New Jersey, on January 8, 1918. He studied meteorology at New York University while in the Army Air Corps during World War II, and then was engaged in radio wave propagation studies until the war ended. After the war, he continued these studies at the University of Texas in Austin, and in 1948 moved to Ithaca, New York, for graduate study in electrical engineering at Cornell. He stayed at Cornell after obtaining his Ph.D. degree in 1953. In 1958 he conceived of a large vertically directed radar to measure the electron density and temperature in the high ionosphere. This became the Arecibo project, whose study and construction in Puerto Rico he organized, and the giant system was dedicated in 1963. He became its first director. In 1965 he moved to Rice University as dean of science and engineering, later provost and vice president. He was active in ionospheric research into the 1990s. He died in Ithaca, New York, in February 2010; his survivors include two children, Nancy Ward and Larry Gordon; four grandchildren; three great-grandchildren; and his wife, Elizabeth Bolgiano Gordon of Ithaca. His first wife of 61 years, Elva Gordon, died in 2001.
BibTeX:
@article{Cohen2011,
  author = {Cohen, Marshall H and Lane, Neil F},
  title = {William Edwin Gordon 1918-2010},
  journal = {NAS Biographical Memoir},
  publisher = {National Academy of Sciences},
  year = {2011},
  volume = {n/a-n/a},
  pages = {22 pages},
  url = {http://nas.nasonline.org/site/DocServer/Gordon_William.pdf?docID=77361}
}
da Costa AM, Domingues MO, Mendes O and Brum CGM (2011), "Interplanetary medium condition effects in the South Atlantic Magnetic Anomaly: A case study ", Journal of Atmospheric and Solar-Terrestrial Physics. Vol. 73(11-12), pp. 1478-1491.
Abstract: One way to investigate the magnetosphere–ionosphere coupling is through the simultaneous observation of different parameters measured at different locations of the geospace environment and try to determine some relationships among them. The main objective of this work is to examine how the solar energetic particles and the interplanetary medium conditions may affect the space and time configuration of the ring current at low-latitudes and also to get a better understanding on how these particles interfere with the lower ionosphere in the South Atlantic Magnetic Anomaly region (SAMA). To accomplish this, the cosmic noise absorption (CNA) and the horizontal component of the Earth's magnetic field data measured from sites located in the SAMA region were compared with the proton and electron fluxes, interplanetary medium conditions (solar wind and the north–south component of the interplanetary magnetic field measured on board satellites), the SYM-H index and magnetometer data from Kakioka (KAK-Japan), located significantly outside the SAMA region. The time series analyzed correspond to the geomagnetic disturbance that occurred on August 25-30, 1998. The analysis was performed by implementing wavelet techniques, with particular attention to singularities detection, which highlights the presence of transient signals. The results are discussed in terms of the first three wavelet decomposition levels of the parameters. The magnitude of wavelet coefficients of the solar wind and proton flux at the two energy ranges analyzed is timely well correlated, indicating that these two signals are energetically linked. The larger wavelet coefficient amplitude of KAK and VSS magnetograms shows time delays that are compatible with an asymmetric configuration of the ring current, considering that at the storm time, VSS was at the dawn sector of the magnetosphere and KAK at the dusk side. The wavelet analysis of CNA signals reveals that the signal may be sensitive to the ionization produced by energetic electrons and protons as well. The time delays observed in wavelet coefficients may give an indication of the different accelerating process to which the particles are submitted when traveling along the magnetic field lines, from higher to lower latitudes, and the likely contribution of these particles to the ionization measured as an absorption of the cosmic noise in the lower ionosphere.
BibTeX:
@article{Costa2011,
  author = {Aracy Mendes da Costa and Margarete Oliveira Domingues and Odim Mendes and Christiano Garnett Marques Brum},
  title = {Interplanetary medium condition effects in the South Atlantic Magnetic Anomaly: A case study },
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
  year = {2011},
  volume = {73},
  number = {11-12},
  pages = {1478-1491},
  note = {Arecibo author},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682611000113},
  doi = {10.1016/j.jastp.2011.01.010}
}
Cotts BRT (2011), "Global Quantification of Lighting-Induced Electron Precipition Using Very Low Frequency Remote Sensing". Thesis at: STANFORD UNIVERSITY., 03/2011, 2011.
Review: Observations of lightning-induced electron precipitation (LEP) events at three geographic regions show characteristics which systematically vary with both longitude and hemisphere. These observations are quantitatively interpreted with the use of a novel model of atmospheric backscatter designed to be used to predict the characteristics of LEP events at any longitude and mid-latitude L-shell by accounting for the effects of precipitating electrons which are backscattered from the atmosphere.

The new model of atmospheric backscatter (ABS) is based upon the calculation of ~16,000 individual atmospheric backscatter responses for monoenergetic, monodirectional electron beams with a single incident pitch angle using a Monte Carlo model of atmospheric interactions. The model tracks the full gyration of each individual precipitating electron around the magnetic field line as it enters the atmosphere, accounting for the dynamic friction force and angular diffusion as well as the production of new electrons via ionization. The ABS model includes the effects of the asymmetric magnetic field in calculations of the pitch angle of backscattered electrons entering the conjugate hemisphere and accounts for the different strength of the magnetic field at conjugate points of the same field line. This magnetic field difference causes the equatorial loss cone angle to vary greatly between hemispheres and with longitude, which results in significant and systematic differences in LEP signatures at various locations.

A realistic distribution of precipitating electrons is inserted into the ABS model by calculating the energy and pitch angle distribution, which results from the resonant interactions of a lightning-initiated magnetospherically reflecting whistler wave with trapped radiation belt particles. This calculation is accomplished by extensive magnetospheric ray-tracing, accounting for Landau damping as well as spatial and temporal dispersion of the whistler wave.

This distribution of precipitating electrons is then inserted into the ABS model at three separate longitudes ('N1=260_ E/N, 'N2=290_ E/N, and 'S1=295_ E/S, corresponding to the Central United States, the East Coast of the United States, and Palmer, Antarctica, respectively) and the deposition results are compared with VLF remote sensing data collected on nearly north-south great circle paths (GCPs) allowing for isolation of longitudinal effects on LEP. Results predicted by the model and confirmed by data indicate that all four primary LEP characteristics exhibit longitudinal and hemispheric dependencies which can be explained in terms of backscatter of precipitating electrons from the atmosphere. The mean observed LEP onset delay (Dt) exhibits a hemispheric dependence at these longitudes with events in the northern hemisphere delayed by one bounce period relative to direct precipitation and advanced by one-half bounce period in the southern hemisphere. The mean observed onset duration (td) exhibits a longitudinal dependence with events observed at 'N1 and 'S2 persisting for three bounce periods, and at 'N2for two bounce periods. The amplitude change (DA) and recovery time (tr) also show a longitudinal and hemispheric dependence based upon the relative sizes of the loss cones at different longitudes. LEP events produced at 'N1 have consistently larger perturbation magnitudes than at 'N2 , and observed recovery times at 'N2 are longer than at 'N1 which are still longer than at 'S2 . All of these results are explained in terms of backscatter of precipitating electrons from the atmosphere and the ABS model shows that by accounting for atmospheric backscatter it is possible to accurately predict all the observable characteristics of LEP events. Furthermore, by combining these effects with previously calculated radiation belt electron loss rates due to lightning at a single location, it is possible to estimate the global loss of radiation belt electrons due to lightning.

BibTeX:
@phdthesis{Cotts2011,
  author = {Cotts, Benjamin R. T.},
  title = {Global Quantification of Lighting-Induced Electron Precipition Using Very Low Frequency Remote Sensing},
  school = {STANFORD UNIVERSITY},
  year = {2011},
  url = {http://vlf.stanford.edu/sites/default/files/publications/Cotts_Thesis_OnlineVersion.pdf}
}
Eccles V, Thompson J, Sojka JJ, Vo H and Gonzalez S (2011), "Assessment of Ionospheric Models package for the Community Coordinated Modeling Center: Climatology", Space Weather. Vol. 9(1), pp. n/a-n/a.
Abstract: Due to the paucity of ionospheric density observations, ionospheric models are important for constructing the day-to-day 3-D specifications of electron density. Quality specifications are required to mitigate ionospheric influences on modern GPS navigation and communications technologies. The Arecibo Radar Observatory Incoherent Scatter Radar has provided F region electron density profiles spanning 50 years and 4 solar cycles. We have collected, reduced, and cleaned the Arecibo radar electron density profiles to create a "ground truth database" for use in the metric assessment of the accuracy of empirical and physics-based ionospheric models. The metrics and skill assessments within this Assessment of Ionospheric Models package are described herein. The assessment package will be implemented at the Community Coordinated Modeling Center to provide a Web-based generator of metrics and skill scores based on several electron density profile parameters: peak density values, peak density altitudes, and the shape of the electron density profile with altitude. This Assessment of Ionospheric Models package will greatly assist in improving current models of the ionosphere.
BibTeX:
@article{Eccles2011,
  author = {Eccles, Vince and Thompson, Jonathan and Sojka, Jan J. and Vo, Hien and Gonzalez, Sixto},
  title = {Assessment of Ionospheric Models package for the Community Coordinated Modeling Center: Climatology},
  journal = {Space Weather},
  year = {2011},
  volume = {9},
  number = {1},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2010SW000596},
  doi = {10.1029/2010SW000596}
}
Eccles V, Vo H, Thompson J, Gonzalez S and Sojka JJ (2011), "Database of electron density profiles from Arecibo Radar Observatory for the assessment of ionospheric models", Space Weather. Vol. 9(1), pp. n/a-n/a.
Abstract: We describe the reduction of the Arecibo Observatory incoherent scatter radar electron density profiles from 1966 to 2006 into a standardized database of electron density profiles useful for the assessment of ionospheric models. The database of electron density profiles covers approximately 700 days of observation over nearly 4 solar cycles and all seasons. These data are averaged into climatological conditions with special attention at maintaining a normal profile shape in altitude. The reduced profile database and the climatological average profiles are provided to the Community Coordinated Modeling Center for open access by the community and their efforts to generate ionosphere model metrics and skill scores.
BibTeX:
@article{Eccles2011a,
  author = {Eccles, Vince and Vo, Hien and Thompson, Jonathan and Gonzalez, Sixto and Sojka, Jan J.},
  title = {Database of electron density profiles from Arecibo Radar Observatory for the assessment of ionospheric models},
  journal = {Space Weather},
  year = {2011},
  volume = {9},
  number = {1},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2010SW000591},
  doi = {10.1029/2010SW000591}
}
Balcerak E (2011), "Currents can be driven in the polar ionosphere", Eos, Transactions American Geophysical Union. Vol. 92(31), pp. 264-264.
Abstract: The study of ionospheric heaters that induce controlled modifications in the ionosphere allows better understanding of effects driven naturally by solar activity in the ionosphere and the radiation belts. Previous ionospheric heaters at the Earth's poles have generated ultralow-frequency, extremely low frequency, and very low frequency waves in the ionosphere's D andE regions by modulating the auroral electrojet, the strong horizontal currents that naturally flow in the D and E regions at high latitudes. Now Papadopoulos et al. present theoretical and computational results that indicate that using high-frequency heating, low-frequency ionospheric currents can also be generated at F region altitudes, independent of the presence or absence of electrojet currents. The new technique, whose validity has been confirmed tentatively in recent polar experiments, allows generation of low-frequency waves by midlatitude heaters, such as the one under construction in Arecibo, Puerto Rico, and their subsequent injection in the inner radiation belt. It will permit for the first time the study of the interaction of artificially generated low-frequency waves with multi-MeV protons trapped in the inner belt and their precipitation rates in the South Atlantic anomaly region. (Geophysical Research Letters, doi:10.1029/2011GL047368, 2011)
BibTeX:
@article{EOST:EOST17996,
  author = {Balcerak, Ernie},
  title = {Currents can be driven in the polar ionosphere},
  journal = {Eos, Transactions American Geophysical Union},
  year = {2011},
  volume = {92},
  number = {31},
  pages = {264--264},
  url = {http://dx.doi.org/10.1029/2011EO310007},
  doi = {10.1029/2011EO310007}
}
Fentzke JT, Sulzer MP and Gonzalez SA (2011), "The effects of Bhatnagar-Gross-Krook, Brownian, and hard-sphere ion-neutral collision models on the incoherent scatter spectrum in the E region", Journal of Geophysical Research: Space Physics. Vol. 116(A1), pp. n/a-n/a.
Abstract: We revisit the theory developed by Hagfors and Brockelman (1971). The purpose of this work is to improve the understanding of variations in the incoherent scatter spectrum in the lower E region of the ionosphere between approximately 85 and 150 km under the assumption of Brownian, Bhatnagar-Gross-Krook, and hard-sphere collisions in the absence of magnetic field influences, for operating frequencies representative of the chain of NSF-sponsored incoherent scatter radars (ISRs), which range from 50 to 1290 MHz. Also, we extend the computationally limited examples in Hagfors and Brockelman (1971) as well as demonstrate the feasibility of making the E region measurements at the Arecibo Observatory ISR in Puerto Rico (18°N, 67°W). We confirm the theory from Hagfors and Brockelman (1971) and show that the original nondimensionalized examples were representative of spectra at approximately 95, 105, and 150 km. Additionally, our results show that there is more variability in the incoherent scatter spectrum for the aforementioned ion-neutral collision approximations, especially in the 90–105 km altitude range compared to the results shown by Hagfors and Brockelman (1971). This is most likely due to the greater computational resources currently available and the more up-to-date models for atmospheric and ionospheric conditions derived from MSIS-00 and IRI-07, respectively. These findings suggest that future work is needed to evaluate the impact, if any, on the ionospheric parameters derived using each of the three ion-neutral collision approximations.
BibTeX:
@article{Fentzke2011,
  author = {Fentzke, J. T. and Sulzer, M. P. and Gonzalez, S. A.},
  title = {The effects of Bhatnagar-Gross-Krook, Brownian, and hard-sphere ion-neutral collision models on the incoherent scatter spectrum in the E region},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2011},
  volume = {116},
  number = {A1},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2010JA015340},
  doi = {10.1029/2010JA015340}
}
Garzon DP, Brum CGM, Echer E, Aponte N, Sulzer MP, Gonzalez SA, Kerr RB and Waldrop L (2011), "Response of the topside ionosphere over Arecibo to a moderate geomagnetic storm", Journal of Atmospheric and Solar-Terrestrial Physics. Vol. 73(11-12), pp. 1568-1574.
Abstract: We analyze the data obtained using the Arecibo incoherent scatter radar to examine the response of the topside ionosphere to a moderate geomagnetic storm that occurred during the period March 7-11, 2008. During this time period a magnetic storm with a non-monotonic main phase decrease in the Dst index occurred. The recovery phase also exhibited a secondary Dst decrease. During the initial phase of the storm, Te and Ti increased coincident with the arrival of the solar wind. The main phase registered an increase in proton concentration proportional to Ne while temperatures reached the lowest values. Variations in O+ concentration were not significant but a reduction in helium fraction was observed. Soon after the peak of the storm, the transition height between the topside ionosphere and the protonosphere, where H+ ions dominate composition, was lower than would be expected during quiet conditions and this behavior lasted for approximately 12h.
BibTeX:
@article{Garzon2011,
  author = {Diana Prado Garzon and Christiano Garnett Marques Brum and Ezequiel Echer and Nestor Aponte and Michael P. Sulzer and Sixto A. Gonzalez and Robert B. Kerr and Lara Waldrop},
  title = {Response of the topside ionosphere over Arecibo to a moderate geomagnetic storm},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
  year = {2011},
  volume = {73},
  number = {11-12},
  pages = {1568-1574},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682611000630},
  doi = {10.1016/j.jastp.2011.02.016}
}
Gong Y and Zhou Q (2011), "Incoherent scatter radar study of the terdiurnal tide in the E- and F-region heights at Arecibo", Geophysical Research Letters. Vol. 38(15), pp. n/a-n/a.
Abstract: We report the analysis of the terdiurnal tide in the meridional wind from 90 to 350 km at a low latitude station. Our data is based on nine days of consecutive observation made by the Arecibo incoherent scatter radar during January 14–23, 2010. The terdiurnal tide is observed to be prominent at E-region heights in the first four days (Jan. 14–18) and at the F-region heights in the last five days (Jan. 18–23). The terdiurnal tide is among the two strongest tidal components in both regions. The vertical wavelength of the terdiurnal tide is about 100 km, and 950 km, for the altitude range of 128 to 142 km, and 180 to 320 km, respectively. The F-region terdiurnal tide amplitude is found to be well correlated with the background meridional wind in the lower F-region. Our analysis does not reveal any evidence that non-linear interaction between diurnal and semidiurnal tides is important for the F-region terdiurnal tide.
BibTeX:
@article{Gong2011,
  author = {Gong, Yun and Zhou, Qihou},
  title = {Incoherent scatter radar study of the terdiurnal tide in the E- and F-region heights at Arecibo},
  journal = {Geophysical Research Letters},
  year = {2011},
  volume = {38},
  number = {15},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2011GL048318},
  doi = {10.1029/2011GL048318}
}
Papadopoulos K, Gumerov NA, Shao X, Doxas I and Chang CL (2011), "HF-driven currents in the polar ionosphere", Geophysical Research Letters. Vol. 38(12), pp. n/a-n/a.
Abstract: Polar ionospheric heaters have generated ULF/ELF/VLF waves by modulating the auroral electrojet at D/E region altitudes. We present theoretical/computational results indicating that modulated F-region HF heating can generate ionospheric currents even in the absence of electrojet currents. The ELF currents are driven in a two-step process. First, the pressure gradient associated with F-region electron heating drives a local diamagnetic current. This acts as an antenna to inject Magneto-Sonic (MS) waves in the ionospheric plasma. Second, the electric field of the magneto-sonic wave drives Hall currents when it reaches the E region of the ionosphere. The Hall currents act as a secondary antenna that injects waves in the Earth-Ionosphere Waveguide below and Shear Alfven waves upwards to the conjugate regions. The paper examines the scaling and limitations of the concept and suggests proof-of-principle experiments using the HAARP ionospheric heater.
BibTeX:
@article{GRL:GRL28066,
  author = {Papadopoulos, K. and Gumerov, N. A. and Shao, X. and Doxas, I. and Chang, C. L.},
  title = {HF-driven currents in the polar ionosphere},
  journal = {Geophysical Research Letters},
  year = {2011},
  volume = {38},
  number = {12},
  pages = {n/a--n/a},
  url = {http://dx.doi.org/10.1029/2011GL047368},
  doi = {10.1029/2011GL047368}
}
Hysell DL, Yokoyama T, Nossa E, Hedden RB, Larsen MF, Munro J, Smith S, Sulzer MP and Gonzalez SA (2011), "Radar and Optical Observations of IrregularMidlatitude Sporadic E Layers Beneath MSTIDs", Aeronomy of the Earth, Atmosphere and Ionosphere. Vol. 19, pp. 269-281.
Abstract: An irregular sporadic E ionization layer was observed by the Arecibo incoherent scatter radar and a coherent scatter radar imager located on St. Croix during the passage of an MSTID observed by the Boston University all-sky camera in 630 nm imagery. The MSTID in question was not very intense and was barely detectable in the vertical F region plasma drifts measured by Arecibo. The intensity of the coherent scatter from small-scale irregularities in the sporadic E layer appeared nonetheless to be modulated by the MSTID and was strongest in the F region airglow crests, mapped along magnetic field lines to the E region volume being observed. The coherent scatter Doppler shifts were highly correlated with altitude displacements in the sporadic E layer, and the sign of the correlation was controlled by the sign of the background zonal electric field. The MSTID did not appear to modulate the morphology of the sporadic E layer irregularities themselves, which took the form of convective rolls and which drifted with the ambient neutral wind.
BibTeX:
@article{Hysell2011,
  author = {David L. Hysell and Tatsuhiro Yokoyama and Eliana Nossa and Russell B. Hedden and Miguel F. Larsen and John Munro and Steven Smith and Michael P. Sulzer and and Sixto A. Gonzalez},
  title = {Radar and Optical Observations of IrregularMidlatitude Sporadic E Layers Beneath MSTIDs},
  journal = {Aeronomy of the Earth, Atmosphere and Ionosphere},
  year = {2011},
  volume = {19},
  pages = {269-281},
  doi = {10.1007/978-94-007-0326-1_19}
}
Klimenko MV, Klimenko VV, Ratovsky KG, Goncharenko LP, Sahai Y, Fagundes PR, de Jesus R, de Abreu AJ and Vesnin AM (2011), "Numerical modeling of ionospheric effects in the middle- and low-latitude F region during geomagnetic storm sequence of 9-14 September 2005", Radio Science. Vol. 46(3), pp. n/a-n/a.
Abstract: This study presents the Global Self-Consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) numerical simulations of the 9–14 September 2005 geomagnetic storm effects in the middle- and low-latitude ionosphere. Recent modifications to the GSM TIP model include adding an empirical model of high-energy electron precipitation and introducing a high-resolution (1 min) calculation of region 2 field-aligned currents and a cross-cap potential difference. These modifications resulted in better representation of such effects as penetration of the magnetospheric convection electric field to lower latitudes and the overshielding. The model also includes simulation of solar flare effects. Comparison of model results with observational data at Millstone Hill (42.6°N, 71.5°W, USA), Arecibo (18.3°N, 66.8°W, Puerto Rico), Jicamarca (11.9°S, 76.9°W, Peru), Palmas (10.2°S, 48.2°W, Brazil), and San Jose Campos (23.2°S, 45.9°W, Brazil) shows good agreement of ionospheric disturbances caused by this storm sequence. In this paper we consider in detail the formation mechanism of the additional layers in an equatorial ionosphere during geomagnetic storms. During geomagnetic storms, the nonuniform in height zonal electric field is generated at the geomagnetic equator. This electric field forms the additional layers in the F region of equatorial ionosphere.
BibTeX:
@article{Klimenko2011,
  author = {Klimenko, M. V. and Klimenko, V. V. and Ratovsky, K. G. and Goncharenko, L. P. and Sahai, Y. and Fagundes, P. R. and de Jesus, R. and de Abreu, A. J. and Vesnin, A. M.},
  title = {Numerical modeling of ionospheric effects in the middle- and low-latitude F region during geomagnetic storm sequence of 9-14 September 2005},
  journal = {Radio Science},
  year = {2011},
  volume = {46},
  number = {3},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2010RS004590},
  doi = {10.1029/2010RS004590}
}
Klimenko MV, Klimenko VV, Ratovskii KG and Goncharenko LP (2011), "Ionospheric effects of geomagnetic storms at mid latitudes", Russian Journal of Physical Chemistry B, Focus on Physics. Vol. 5, pp. 24-34.
Abstract: Previously, we studied the ionospheric effects of the sequence of geomagnetic storms on September 9–14, 2005 using a global self-consistent model “Thermosphere-Ionosphere-Protonosphere” (GSM TIP). Differences between the predicted and observed effects of the ionospheric storms may be due to the use of the three-hour K p index of geomagnetic activity in modeling the time dependence of model input parameters, use of the dipole approximation of the geomagnetic field, and disregard in simulations for solar flares that occurred during this period. We tried to eliminate two of these three reasons. First, we used the A E index of geomagnetic activity with minute resolution in modeling the time dependence of the model input parameters. Second, we took into account the effects of solar flares. In addition, GSM TIP model was supplemented by an empirical model describing the precipitation of high-energy electrons. The results of the simulation of the behavior of various ionospheric parameters over the Yakutsk, Irkutsk, Millstone Hill, and Arecibo stations on September 9 and 10, 2005 in the new formulation of the problem, presented in the current work, are in better agreement with the available experimental data than the results of previous calculations.
BibTeX:
@article{Klimenko2011a,
  author = {Klimenko, M V and Klimenko, V V and Ratovskii, K G and Goncharenko, L P},
  title = {Ionospheric effects of geomagnetic storms at mid latitudes},
  journal = {Russian Journal of Physical Chemistry B, Focus on Physics},
  year = {2011},
  volume = {5},
  pages = {24-34},
  doi = {10.1134/s1990793111030092}
}
Klimenko MV, Klimenko VV, Ratovsky KG and Goncharenkod LP (2011), "Ionospheric Effects Caused by the Series of Geomagnetic Storms of September 9-14, 2005", Geomagnetism and Aeronomy. Vol. 51, pp. 368-380.
Abstract: This study presents the ionospheric effects caused by the series of geomagnetic storms of September 9–14, 2005. The behavior of different ionospheric parameters over the Yakutsk, Irkutsk, Millstone Hill and Arecibo stations during the considered period have been numerically calculated, using a global self-consistent model of the thermosphere, ionosphere, and protonosphere (GSM TIP) developed at WD IZMI-RAN. The model calculations of disturbances of the ionospheric parameters during storms qualitatively agree with the experimental data at these midlatitude stations. We suggest that the causes of the quantitative differences between the model calculations and the observational data were the use of the 3-hour Kp index of geomagnetic activity and the dipole approximation of geomagnetic field in GSM TIP, with additional contributions from the effects of solar flares which are not considered in GSM TIP.
BibTeX:
@article{Klimenko2011b,
  author = {M. V. Klimenko and V. V. Klimenko and K. G. Ratovsky and L. P. Goncharenkod},
  title = {Ionospheric Effects Caused by the Series of Geomagnetic Storms of September 9-14, 2005},
  journal = {Geomagnetism and Aeronomy},
  year = {2011},
  volume = {51},
  pages = {368-380},
  url = {http://dx.doi.org/10.1134/S0016793211030108},
  doi = {10.1134/S0016793211030108}
}
Mann I, Pellinen-Wannberg A, Murad E, Popova O, Meyer-Vernet N, Rosenberg M, Mukai T, Czechowski A, Mukai S, Safrankova J and Nemecek Z (2011), "Dusty Plasma Effects in Near Earth Space and Interplanetary Medium", Space Science Reviews. Vol. 161(1-4), pp. 1-47.
Abstract: We review dust and meteoroid fluxes and their dusty plasma effects in the interplanetary medium near Earth orbit and in the Earth’s ionosphere. Aside from in-situ measurements from sounding rockets and spacecraft, experimental data cover radar and optical observations of meteors. Dust plasma interactions in the interplanetary medium are observed by the detection of charged dust particles, by the detection of dust that is accelerated in the solar wind and by the detection of ions and neutrals that are released from the dust. These interactions are not well understood and lack quantitative description. There is still a huge discrepancy in the estimates of meteoroid mass deposition into the atmosphere. The radar meteor observations are of particular interest for determining this number. Dust measurements from spacecraft require a better understanding of the dust impact ionization process, as well as of the dust charging processes. The latter are also important for further studying nanodust trajectories in the solar wind. Moreover understanding of the complex dependencies that cause the variation of nanodust fluxes is still a challenge.
BibTeX:
@article{Mann2011,
  author = {Mann, Ingrid and Pellinen-Wannberg, Asta and Murad, Edmond and Popova, Olga and Meyer-Vernet, Nicole and Rosenberg, Marlene and Mukai, Tadashi and Czechowski, Andrzej and Mukai, Sonoyo and Safrankova, Jana and Nemecek, Zdenek},
  title = {Dusty Plasma Effects in Near Earth Space and Interplanetary Medium},
  journal = {Space Science Reviews},
  year = {2011},
  volume = {161},
  number = {1-4},
  pages = {1-47},
  doi = {10.1007/s11214-011-9762-3}
}
Martinis C, Baumgardner J, Wroten J and Mendillo M (2011), "All-sky imaging observations of conjugate medium-scale traveling ionospheric disturbances in the American sector", Journal of Geophysical Research: Space Physics. Vol. 116(A5), pp. A05326 (7p).
Abstract: All-sky imaging systems at Arecibo, Puerto Rico (18.3°N, 66.7°W, +28° mag. lat.), and Mercedes, Argentina (34.6°S, 59.4°W, ?24.6° mag. lat.), are used to study ionospheric conjugate processes at lower midlatitudes. For the first time in the American sector the simultaneous occurrence in both hemispheres of medium-scale traveling ionospheric disturbances has been observed. The first year of observations yielded 43 nights (?40%) with simultaneous occurrence of airglow bands. Supporting information from GPS receivers indicate the presence of vertical total electron content variations that correlate with the airglow structures observed with the imagers. Weak phase fluctuations have been measured, indicating that these structures do not produce severe large-scale ionospheric irregularities.
BibTeX:
@article{Martinis2011,
  author = {Martinis, C. and Baumgardner, J. and Wroten, J. and Mendillo, M.},
  title = {All-sky imaging observations of conjugate medium-scale traveling ionospheric disturbances in the American sector},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2011},
  volume = {116},
  number = {A5},
  pages = {A05326 (7p)},
  doi = {10.1029/2010JA016264}
}
Pavlov AV and Pavlova NM (2011), "Comparison of modeled electron densities and electron and ion temperatures with Arecibo observations during undisturbed and geomagnetic storm periods of 7-11 September 2005", Journal of Geophysical Research: Space Physics. Vol. 116(A3), pp. n/a-n/a.
Abstract: The electron density and the electron and ion temperatures measured by the Arecibo radar at 496 km altitude and NmF2 observed by the Puerto Rico ionosonde are compared with those produced by the model of the ionosphere and plasmasphere to study the time-dependent response of the ionosphere to geomagnetic forcing during the undisturbed and geomagnetic storm periods of 7–11 September 2005. The reasonable agreement between the model results and data requires the modified HWM90 wind and the modified NRLMSISE-00 neutral temperature. The pronounced positive daytime storm changes in NmF2 are created by increases in the upward wind-induced plasma drift due to the neutral wind, while the geomagnetic storm decreases in [N2] and [O2] and the enhanced disturbed upward wind-induced plasma drift cause the pronounced positive nighttime disturbances in NmF2. The storm neutral wind-induced plasma drift and neutral composition changes are responsible for the pronounced negative daytime NmF2 disturbances. The F2 layer transport from lower to higher altitudes by the upward wind-induced plasma drift decreases the distance between the hmF2 and our chosen altitude for study of the topside ionosphere. This results in the increase of the electron density at this chosen altitude due to a more weakly reduction in the electron density with altitude. The pronounced postmidnight peaks observed in the topside electron density over Arecibo are provided by these increases in the electron density
BibTeX:
@article{Pavlov2011,
  author = {Pavlov, A. V. and Pavlova, N. M.},
  title = {Comparison of modeled electron densities and electron and ion temperatures with Arecibo observations during undisturbed and geomagnetic storm periods of 7-11 September 2005},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2011},
  volume = {116},
  number = {A3},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2010JA016067},
  doi = {10.1029/2010JA016067}
}
Raizada S, Tepley CA, Aponte N and Cabassa E (2011), "Characteristics of neutral calcium and Ca+ near the mesopause, and their relationship with sporadic ion/electron layers at Arecibo", Geophysical Research Letters. Vol. 38(9), pp. n/a-n/a.
Abstract: We present the first simultaneous observations of mesospheric neutral calcium, its ion, and electron density over Arecibo obtained on adjacent nights in December 2009. A good correlation is seen between Sporadic-E and ion layers while the neutrals have different characteristics. The measurements reveal that average abundances in electron densities and ions to be at a maximum on 9 December with values ~4.8 × 109 electrons cm-2 and 3.4 × 107 ions cm-2, while those of the neutrals to be low, of the order of 9.7 × 106 atoms cm-2. The neutral abundance maximizes with values of 1.8 × 107 atoms cm-2 on 10 December, when both ions and electrons display weak layers with abundances almost 3 times lower than on the previous night. A significant correlation between the ions and neutrals indicates that sudden enhancements are caused by advection while a poor correlation is related to chemistry. This study reveals that the ion-neutral coupling is most efficient between 92 and 95 km. Also, the ion-to-neutral ratio is dependent on the strength of the ions or Sporadic-E and can exceed 3.0 during such events. We present evidence of neutralization of the ionized layers occurring on scales of a few tens of minutes for the first time. This agrees fairly well with the lifetimes of Ca+ against neutralization as predicted by recent ion-neutral reactions.
BibTeX:
@article{Raizada2011,
  author = {Raizada, Shikha and Tepley, Craig A. and Aponte, Nestor and Cabassa, Edvier},
  title = {Characteristics of neutral calcium and Ca+ near the mesopause, and their relationship with sporadic ion/electron layers at Arecibo},
  journal = {Geophysical Research Letters},
  year = {2011},
  volume = {38},
  number = {9},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2011GL047327},
  doi = {10.1029/2011GL047327}
}
Santos PT, Brum CGM, Tepley CA, Aponte N, Gonzalez SA and Robles E (2011), "Using incoherent scatter radar to investigate the neutral wind long-term trend over Arecibo", Journal of Geophysical Research: Space Physics. Vol. 116(A2), pp. A00H13 (9 pages).
Abstract: Thermospheric neutral winds can be the most important driver when modeling ionospheric densities and temperatures. Several papers in this special edition show interesting features of the neutral winds behavior during the last 30 years at the Arecibo Observatory (18.3N, 66.75W; 28.25 dip latitude) using Fabry-Perot Interferometer (FPI) data. A neutral wind vector that changes its direction, becoming more dominantly eastward over the years and a meridional neutral wind component that decreases in magnitude, were found. The main goal of this work is to look for similar evidence of long-term trends in the radar derived winds that might support these recent discoveries and explore the associated ionospheric parameter measurements to look for the effects of these changing winds on the ionosphere. With this purpose in mind, Incoherent Scatter Radar (ISR) measurements of the F region vector drifts are used to derive the corresponding meridional thermospheric neutral wind along the magnetic field over Arecibo during 20 years. Major findings include a decreasing long-term trend (lowering) of the height where the F2- layer peak density occurs (hmF2), which could be related with a more increased downward flux of the ionosphere. A slight decrease in the peak density of the F2- layer (NmF2) after local midnight also was found during the period studied. The meridional wind along the magnetic field derived from ISR data also revealed a long-term trend, becoming more northward during the period studied, with a maximum variation between 02:30UT and 05:30UT.
BibTeX:
@article{Santos2011,
  author = {Santos, P. T. and Brum, C. G. M. and Tepley, C. A. and Aponte, N. and Gonzalez, S. A. and Robles, E.},
  title = {Using incoherent scatter radar to investigate the neutral wind long-term trend over Arecibo},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2011},
  volume = {116},
  number = {A2},
  pages = {A00H13 (9 pages)},
  url = {http://dx.doi.org/10.1029/2011JA016514},
  doi = {10.1029/2011JA016514}
}
Seker I, Fung SF and Mathews JD (2011), "Relation between magnetospheric state parameters and the occurrence of plasma depletion events in the nighttime midlatitude F region", Journal of Geophysical Research: Space Physics. Vol. 116, pp. 4323.
Abstract: Studies using all-sky imagers have revealed the presence of various ionospheric irregularities in the nighttime midlatitude F region. The most prevalent and well known of these are the medium-scale traveling ionospheric disturbances (MSTIDs) that usually occur when the geomagnetic activity is low and midlatitude spread F plumes that are often observed when the geomagnetic activity is high. The inverse and direct relations between geomagnetic activity and the occurrence rate of MSTIDs and midlatitude plumes, respectively, have been observed by several studies using different instruments; however, most of them focus on MSTIDs only and use only Kp to characterize geomagnetic activity. In order to understand the underlying causes of these two relations and to distinguish between MSTIDs and plumes, it is illuminating to better characterize the occurrence of MSTIDs and plumes using multiple magnetospheric state parameters. Here we statistically compare multiple geomagnetic driver and response parameters (such as Kp, AE, Dst, and solar wind parameters) with the occurrence rates of nighttime MSTIDs and plumes observed using an all-sky imager at Arecibo Observatory (AO) between 2003 and 2008. We also present seasonal and annual variations of MSTIDs and plumes at AO. The results not only allow us to better distinguish MSTIDs and plumes, but also to shed further light on the generation mechanism and electrodynamics of these two different phenomena occurring at nighttime in the midlatitude F region.
BibTeX:
@article{Seker2011,
  author = {Seker, I. and Fung, S. F. and Mathews, J. D.},
  title = {Relation between magnetospheric state parameters and the occurrence of plasma depletion events in the nighttime midlatitude F region},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2011},
  volume = {116},
  pages = {4323},
  url = {http://dx.doi.org/10.1029/2010JA015521},
  doi = {10.1029/2010JA015521}
}
Tepley CA, Robles E, Garcia R, Santos PT, Brum CM and Burnside RG (2011), "Directional trends in thermospheric neutral winds observed at Arecibo during the past three solar cycles", Journal of Geophysical Research: Space Physics. Vol. 116(A2), pp. A00H06 (9 pages).
Abstract: Since 1980, we have observed the thermospheric neutral wind at the Arecibo Observatory using a Fabry-Perot interferometer to measure the O(1D) 630 nm emission. Burnside and Tepley (1989) examined the first 8 years of this extended data set and found that there were no significant or systematic solar cycle influences on the magnitude or direction of the neutral wind field, nor on its horizontal gradients. Such affects have been observed previously at other locations around the globe, and their absence at Arecibo may have been due to the limited data set. Thus, we have extended the period of acquisition and analysis of our neutral wind measurements to include nearly three complete solar cycles (or approximately 30 years) and will present our results within the framework of the earlier work. While the earlier conclusion that no major systematic solar cycle influence on the neutral winds at Arecibo generally remains intact, we did find a slight increase in wind magnitude and a gradual, yet consistent rotation of the thermospheric neutral wind vector from a general southeast to a more eastward flow during 30 years of observation. We explain the magnitude and directional variations in terms of long-term changes in the density and temperature of the upper atmosphere and their possible dissimilar influences on each wind component that appear as a rotation of the neutral wind vector.
BibTeX:
@article{Tepley2011,
  author = {Tepley, C. A. and Robles, E. and Garcia, R. and Santos, P. T. and Brum, C. M. and Burnside, R. G.},
  title = {Directional trends in thermospheric neutral winds observed at Arecibo during the past three solar cycles},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2011},
  volume = {116},
  number = {A2},
  pages = {A00H06 (9 pages)},
  url = {http://dx.doi.org/10.1029/2010JA016172},
  doi = {10.1029/2010JA016172}
}
Zhou QH, Morton YT, Huang CM, Aponte N, Sulzer M and Gonzalez S (2011), "Incoherent scatter radar observation of E-region vertical electric field at Arecibo", Geophysical Research Letters. Vol. 38(1), pp. n/a-n/a.
Abstract: We report the first spatially and temporally continuous observations of the upward electric field in the E-region using the Arecibo incoherent scatter radar. This is achieved by employing the dual beam incoherent scatter radar measurements of ion velocity and using a theoretical ion-neutral collision model. The derived daytime vertical electric field, from ~105 km to 145 km, shows large height variation, as in previous nighttime rocket measurements. Assuming that the electric field along the field line is negligible, the height variation is the same as the horizontal variation at Arecibo. Although the height variation has been attributed to gravity waves in previous studies, this explanation is not consistent with the temporal characteristics in our observation. We further discuss the error sources that affect the measurement of the electric field.
BibTeX:
@article{Zhou2011a,
  author = {Zhou, Q. H. and Morton, Y. T. and Huang, C. M. and Aponte, N. and Sulzer, M. and Gonzalez, S.},
  title = {Incoherent scatter radar observation of E-region vertical electric field at Arecibo},
  journal = {Geophysical Research Letters},
  year = {2011},
  volume = {38},
  number = {1},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2010GL045549},
  doi = {10.1029/2010GL045549}
}
Abdu M, Batista I, Brum CGM, MacDougall J, Santos A, de Souza J and Sobral J (2010), "Solar flux effects on the equatorial evening vertical drift and meridional winds over Brazil: A comparison between observational data and the IRI model and the HWM representations", Advances in Space Research . Vol. 46(8), pp. 1078-1085.
Abstract: We present the results of a study of the equatorial evening F region prereversal vertical drift enhancement over Brazil as a function of solar flux (F10.7). The vertical drift is measured from true heights obtained from digisondes operated at an equatorial site, Sao Luis, and at an off equatorial site, Fortaleza. The different magnetic inclinations of the two sites cause different degree of dependence of the vertical drift on magnetic meridional winds permitting an evaluation of the solar flux control on both the evening vertical drift (zonal electric field) and meridional winds. The analysis period covers the year 2001 and 2004 during which the monthly mean F10.7 varied from 245 to 80. The solar flux dependence of the vertical drift of the evening F layer as obtained from the data are compared with the representation of such dependence in the IRI model. While the IRI description of such dependence appears comparable to that is determined from observational data there is significant difference between the drift values in the two cases, the IRI representation being an under-estimation of the observed drift for all flux values. The results are discussed from the perspective of validating the IRI model representations of the vertical drift. The results of the study also shows that the HWM description of the evening thermospheric meridional wind in the Brazilian sector, shows agreement with observation for lower F10.7 values, while it significantly deviates from the observed/calculated meridional wind for higher solar flux values.
BibTeX:
@article{Abdu2010,
  author = {M.A. Abdu and I.S. Batista and C. G. M. Brum and J.W. MacDougall and A.M. Santos and J.R. de Souza and J.H.A. Sobral},
  title = {Solar flux effects on the equatorial evening vertical drift and meridional winds over Brazil: A comparison between observational data and the IRI model and the HWM representations},
  journal = {Advances in Space Research },
  year = {2010},
  volume = {46},
  number = {8},
  pages = {1078-1085},
  note = {Arecibo author},
  url = {http://www.sciencedirect.com/science/article/pii/S0273117710003923},
  doi = {10.1016/j.asr.2010.06.009}
}
Bhatt A (2010), "Exploring The Electron Component In Incoherent Scatter From The Ionosphere". Thesis at: CORNELL UNIVERSITY.
Review: Small thermally-induced ?uctuation in the ionospheric electron density present a scattering cross-section, if probed with a radar frequency higher than the plasma frequency. This technique, known as the incoherent scattering from the ionosphere, is a well-established ?eld of study now. Since the conception of this ?eld of study in 1958, numerous theoretical and experimental efforts have led the way to the high precision ionospheric research we have today. The theory of the incoherent scatter is highly robust. Recent advances in the radar hardware and computing technology have made it possible to probe the ionosphere using the full extent of this theory. In the effort presented here, high spectral resolution incoherent scatter experiments have been used to, for the ?rst time, fully understand the theoretical predictions concerning the electron component of incoherent scatter. The two resonance lines that constitute the electron component are called the gyro line and the plasma line, and are greatly affected by the presence of the earth’s geomagnetic ?eld. The experiments described here present the ?rst unambiguous measurements of the gyro line with high spectral resolution in the incoherent scatter spectrum. Plasma line experiments presented here show the existence of frequency gaps that were predicted in the early days of incoherent scatter theory, but never observed. High latitude plasma line measurements are presented here to show that using the plasma line technique, the gravity waves in the thermosphere can be detected. The intention here is to observe all the components of the incoherent scatter and apply them to understand ionospheric processes.
BibTeX:
@phdthesis{Bhatt2010,
  author = {Bhatt, Asti},
  title = {Exploring The Electron Component In Incoherent Scatter From The Ionosphere},
  school = {CORNELL UNIVERSITY},
  year = {2010},
  url = {http://hdl.handle.net/1813/14795}
}
Chau JL, Aponte NA, Cabassa E, Sulzer MP, Goncharenko LP and Gonzalez SA (2010), "Quiet time ionospheric variability over Arecibo during sudden stratospheric warming events", Journal of Geophysical Research: Space Physics. Vol. 115(A9), pp. n/a-n/a.
Abstract: We present observations of the F-region ionosphere over Arecibo, Puerto Rico (18.34°N, 66.75°W), during the January–February 2008 and January–February 2009 sudden stratospheric warming (SSW) events. For the first period (2008), we have used incoherent scatter radar (ISR) electron density and temperature measurements from the Arecibo Observatory (AO), as well as relative total electron content (TEC) derived from a dual-frequency GPS receiver. For the second event (2009), during which we observed the largest recorded stratospheric warming, we have used the relative GPS TEC. Our analysis indicates that the ionosphere over Arecibo exhibits perturbations after the SSW, the effects are most visible during the daytime. The strongest signatures are observed in the TEC measurements, represented by large enhancements (with respect to non SSW days), particularly during daytime hours. However, the local time dependence of these enhancements is not the same in the two events. In addition, the data show that our results are consistent with the larger than normal daytime vertical drift differences observed at the magnetic equator over Jicamarca. The electron temperature is also affected during the daytime due to changes in electron density, indicating that the electron temperatures is influenced, indirectly, by changes in planetary wave activity in the lower altitudes.
BibTeX:
@article{Chau2010,
  author = {Chau, J. L. and Aponte, N. A. and Cabassa, E. and Sulzer, M. P. and Goncharenko, L. P. and Gonzalez, S. A.},
  title = {Quiet time ionospheric variability over Arecibo during sudden stratospheric warming events},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2010},
  volume = {115},
  number = {A9},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2010JA015378},
  doi = {10.1029/2010JA015378}
}
Cohen JA, Pradipta R, Burton LM, Labno A, Lee MC, Watkins BJ, Fallen C, Kuo SP, Burke WJ, Mabius D and See BZ (2010), "Generation of ionospheric ducts by the HAARP HF heater", Physica Scripta. Vol. 2010(T142), pp. 014040.
Abstract: We report an investigation of ionospheric ducts having the shape of large plasma sheets, generated by vertically transmitted HAARP HF heater waves in several experiments conducted in Gakona, Alaska. Theory predicts that O-mode heater wave-created ionospheric ducts form parallel-plate waveguides within the meridional plane, and those generated by the X-mode heater waves are orthogonal to the meridional plane. Our theoretical prediction is supported by measurements of ionosonde data (namely ionograms), range–time–intensity (RTI) plots of UHF and HF backscatter radars, as well as magnetometer data analyses. When these plasma sheets experienced E × B drifts, they were intercepted by the HAARP UHF radar and seen as slanted stripes in the RTI plots. This striking feature was also observed in our earlier experiments using the Arecibo UHF radar.
BibTeX:
@article{Cohen2010,
  author = {J A Cohen and R Pradipta and L M Burton and A Labno and M C Lee and B J Watkins and C Fallen and S P Kuo and W J Burke and D Mabius and B Z See},
  title = {Generation of ionospheric ducts by the HAARP HF heater},
  journal = {Physica Scripta},
  year = {2010},
  volume = {2010},
  number = {T142},
  pages = {014040},
  url = {http://stacks.iop.org/1402-4896/2010/i=T142/a=014040},
  doi = {10.1088/0031-8949/2010/T142/014040}
}
Djuth FT, Zhang LD, Livneh DJ, Seker I, Smith SM, Sulzer MP, Mathews JD and Walterscheid RL (2010), "Arecibo's thermospheric gravity waves and the case for an ocean source", Journal of Geophysical Research: Space Physics. Vol. 115(A8), pp. n/a-n/a.
Abstract: Wave-like disturbances in electron density ne have been observed in the thermosphere above Arecibo Observatory, Puerto Rico throughout its 45 year history. However, only recently has it become evident that these waves are continuously present in the Arecibo thermosphere. The wave characteristics are fairly constant between day and night and from season to season. High-resolution electron density measurements obtained by applying the coded long-pulse radar technique to photoelectron-enhanced Langmuir waves are presented. These new observations strongly suggest that the perturbations in electron density are the result of internal acoustic-gravity waves (AGWs) propagating through the Arecibo thermosphere. The AGWs appear to be broadbanded in wave number space. The downward phase trajectories of Dne/ne between 400 and 120 km combined with the low horizontal phase velocities obtained from airglow measurements support the idea that the AGWs are not ducted but rather are locally produced. In addition, the altitudes at which major peaks in Dne/ne are observed follow theoretical estimates for nonducted waves. The nominal period of the AGWs is ?60 min at 250 km altitude, but periods of ~20 min are also evident at lower attitudes. Classic sources of AGWs do not appear to be consistent with the Arecibo observations of a continuous flux of background AGWs. Ray tracing of the AGWs combined with 630.0 nm airglow observations point to a source location in the Atlantic Ocean that is roughly 2100 km east northeast of Arecibo. Internal ocean waves generated in response to the internal tide at the mid-Atlantic Ridge are the most likely source of Arecibo's thermospheric AGWs.
BibTeX:
@article{Djuth2010,
  author = {Djuth, F. T. and Zhang, L. D. and Livneh, D. J. and Seker, I. and Smith, S. M. and Sulzer, M. P. and Mathews, J. D. and Walterscheid, R. L.},
  title = {Arecibo's thermospheric gravity waves and the case for an ocean source},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2010},
  volume = {115},
  number = {A8},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2009JA014799},
  doi = {10.1029/2009JA014799}
}
Erickson P, Goncharenko L, Nicolls M, Ruohoniemi M and Kelley M (2010), "Dynamics of North American sector ionospheric and thermospheric response during the November 2004 superstorm", Journal of Atmospheric and Solar-Terrestrial Physics. Vol. 72(4), pp. 292-301.
Abstract: We present a study of ionospheric and thermospheric response during a November 9–10, 2004 major geomagnetic storm event (DsT ??300 nT). We utilize the North American sector longitude chain of incoherent scatter radars at Arecibo, Millstone Hill, and Sondrestrom, operating as part of a coordinated international mesosphere/lower thermosphere coupling study experiment. Total electron content (TEC) determinations from global positioning system (GPS) ground receivers, ground magnetometer traces from the Canadian CANOPUS array, Defense Meteorological Satellite Platform (DMSP) topside data, and global convection patterns from the SuperDARN radar network are analyzed to place the detailed radar data in proper mesoscale context. The plasmaspheric boundary layer (PBL) expanded greatly in the dusk sector during ring current intensification to span more than 25° of magnetic latitude, reaching as far south as 30° invariant latitude. Strong sub-auroral polarization stream velocities of more than 1 km/s were accompanied by large upwards thermal O+ fluxes to the overlying magnetosphere. The large PBL expansion subsequently exposed both Millstone Hill and Sondrestrom to the auroral convection pattern, which developed a complex multicell and reverse convection response under strongly northward IMF conditions during a period of global interplanetary electric field penetration. Large traveling atmospheric and ionospheric disturbances caused significant neutral wind and ion velocity surges in the mid-latitude and tropical ionosphere and thermosphere, with substorm activity launching equatorward neutral wind enhancements and subsequent mid-latitude dynamo responses at Millstone Hill. However, ionosphere and thermosphere observations at Arecibo point to significant disturbance propagation modification in the post-dusk sector PBL region.
BibTeX:
@article{Erickson2010,
  author = {P.J. Erickson and L.P. Goncharenko and M.J. Nicolls and M. Ruohoniemi and M.C. Kelley},
  title = {Dynamics of North American sector ionospheric and thermospheric response during the November 2004 superstorm},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
  year = {2010},
  volume = {72},
  number = {4},
  pages = {292-301},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682609000881},
  doi = {10.1016/j.jastp.2009.04.001}
}
Angeles ME, González JE, Ramírez-Beltrán ND, Tepley CA and Comarazamy DE (2010), "Origins of the Caribbean Rainfall Bimodal Behavior", Journal of Geophysical Research: Atmospheres. Vol. 115(D11), pp. n/a-n/a.
Abstract: The annual precipitation pattern in the Caribbean basin shows a distinct bimodal behavior, where the first mode is called the Early Rainfall Season (April–July), and the second mode the Late Rainfall Season (August–November). The brief, relatively dry, period in July is usually referred to as the midsummer drought (MSD). It has been hypothesized that the migration through the Caribbean basin of the Intertropical Convergence Zone (ITCZ) and increases in aerosols due to the passing of Saharan Dust across the Caribbean in the summer months may result in the observed precipitation pattern. This paper focuses on determining the origins of the Caribbean MSD. Multiple regression analysis was carried-out to determine if the ITCZ, the North Atlantic Oscillation (NAO) index, the Vertical Wind Shear (VWS), and different atmospheric particle (AP) concentrations transported from northern Africa correlate with the Caribbean MSD. It is shown that the ITCZ and NAO are weakly correlated with the Caribbean precipitation variability; however, the VWS and aerosol particles revealed an important contribution to rainfall during the summer months. Numerical experiments were then performed to quantify the influence of different VWS scenarios and different AP concentrations on the Caribbean precipitation bimodal behavior. The numerical approach uses the Regional Atmospheric Modeling System coupled with a new cloud microphysics module that allows discrimination between small and giant particles, as well as Cloud Concentration Nuclei (CCN) and Giant CCN activation. These numerical experiments support the statistical result that the VWS and the AP influence the rainfall production and pattern during the MSD. Results indicate that cloud microphysics play an important role in producing the observed climatological bimodal pattern, while variations in large-scale atmospheric dynamics (like the VWS) help explain variations in the strength and pattern of the bimodal events and behavior.
BibTeX:
@article{JGRD:JGRD16015,
  author = {Angeles, Moisés E. and González, Jorge E. and Ramírez-Beltrán, Nazario D. and Tepley, Craig A. and Comarazamy, Daniel E.},
  title = {Origins of the Caribbean Rainfall Bimodal Behavior},
  journal = {Journal of Geophysical Research: Atmospheres},
  year = {2010},
  volume = {115},
  number = {D11},
  pages = {n/a--n/a},
  note = {D11106},
  url = {http://dx.doi.org/10.1029/2009JD012990},
  doi = {10.1029/2009JD012990}
}
Kelley MC and Peria WJ (2010), "Interaction of a high-power UHF beam with the ionosphere", Radio Science. Vol. 45(1), pp. n/a-n/a.
Abstract: In 1992 a rocket was launched into a high-power radio beam to study its interaction with the ionosphere. The frequency of the beam, 5.1 MHz, was optimized for such interactions since the frequency used was below the maximum plasma frequency and hence was reflected in a manner that optimized such an interaction. Fortuitously, the rocket passed quite close to the diagnostic Arecibo UHF (430 MHz) radar beam and remarkably, as reported here, we find that there was an interaction as well with the UHF beam. In retrospect, however, we see that the energy density of the UHF radar was more than an order of magnitude higher than the plasma energy density. And, although the quiver velocity of the electrons in the beam is only 4% of their thermal speed, the ponderomotive force is quite a bit larger than the other forces in the medium. This force creates a drift velocity perpendicular to the magnetic field at the beam edge which, we show, is unstable to the drift wave instability and is likely to create the heated ions and fluctuating electric field and plasma density we observe. These results suggest that any transmission of high-power radio waves from a solar power satellite to the ground will interact with the ionosphere in a manner that must be studied before such an expensive project is initiated.
BibTeX:
@article{Kelley2010,
  author = {Kelley, M. C. and Peria, W. J.},
  title = {Interaction of a high-power UHF beam with the ionosphere},
  journal = {Radio Science},
  year = {2010},
  volume = {45},
  number = {1},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2009RS004160},
  doi = {10.1029/2009RS004160}
}
Kelley MC, Ilma RR, Nicolls M, Erickson P, Goncharenko L, Chau JL, Aponte N and Kozyra JU (2010), "Spectacular low- and mid-latitude electrical fields and neutral winds during a superstorm", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 72(4), pp. 285-291.
Abstract: In November 2004, a major magnetic storm occurred, a lengthy portion of which was recorded by the Upper Atmospheric Radar Chain. On the 9th and 10th, the Jicamarca Radar detected the highest magnitude penetrating electric fields (+-3 mV/m) and vertical drifts (±120 m/s) ever seen at this premiere facility. These large and variable drifts were highly correlated with the interplanetary magnetic and electric fields and created a double F layer on the dayside and unusual TEC behavior throughout the low-latitude zone. These solar wind-induced drifts both suppressed and generated irregularities at the magnetic equator at different times. Large-scale thermospheric disturbances were generated by high-latitude heating and tracked through the middle- to low-latitude zones where both parallel and perpendicular plasma drifts created major ionospheric changes. The auroral oval was located at a magnetic L shell of about three for many hours.
BibTeX:
@article{Kelley2010a,
  author = {Michael C. Kelley and Ronald R. Ilma and Michael Nicolls and Philip Erickson and Larisa Goncharenko and Jorge L. Chau and Nestor Aponte and Janet U. Kozyra},
  title = {Spectacular low- and mid-latitude electrical fields and neutral winds during a superstorm},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2010},
  volume = {72},
  number = {4},
  pages = {285-291},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682608003866},
  doi = {10.1016/j.jastp.2008.12.006}
}
Komjathy A, Wilson B, Pi X, Akopian V, Dumett M, Iijima B, Verkhoglyadova O and Mannucci AJ (2010), "JPL/USC GAIM: On the impact of using COSMIC and ground-based GPS measurements to estimate ionospheric parameters", Journal of Geophysical Research: Space Physics. Vol. 115(A2), pp. n/a-n/a.
Abstract: The University of Southern California (USC) and the Jet Propulsion Laboratory (JPL) have jointly developed the Global Assimilative Ionospheric Model (GAIM) to monitor space weather, study storm effects, and provide ionospheric calibration for space weather applications. JPL/USC GAIM is a physics-based 3-D data assimilation model that uses both four-dimensional variational analysis and Kalman-filter techniques to solve for the ion and electron density state and key drivers such as equatorial electrodynamics, neutral winds, and production terms. Here we report on GAIM Kalman filter-based assimilation results using ground-based GPS and COSMIC-derived total electron count (TEC) measurements. We find that assimilating COSMIC measurements into GAIM improves critical ionospheric parameters such as NmF2 and HmF2. Assimilating COSMIC data produces higher-accuracy vertical electron density profile “shapes,” as verified by comparisons to independent electron density profiles measured at Arecibo, Jicamarca, and Millstone Hill incoherent scatter radar (ISR). We also find significant improvement in global vertical TEC (VTEC) maps when assimilating COSMIC measurements, verified by comparing GAIM output with VTEC measurements from the Jason ocean altimeter. For 3 days in June 2006, improvement in accuracy compared to ground-data-only assimilation is found to be 30%, 28%, and 44%, respectively.
BibTeX:
@article{Komjathy2010,
  author = {Komjathy, Attila and Wilson, Brian and Pi, Xiaoqing and Akopian, Vardan and Dumett, Miguel and Iijima, Byron and Verkhoglyadova, Olga and Mannucci, Anthony J.},
  title = {JPL/USC GAIM: On the impact of using COSMIC and ground-based GPS measurements to estimate ionospheric parameters},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2010},
  volume = {115},
  number = {A2},
  pages = {n/a-n/a},
  doi = {10.1029/2009JA014420}
}
Martinis C, Baumgardner J, Wroten J and Mendillo M (2010), "Seasonal dependence of MSTIDs obtained from 630.0 nm airglow imaging at Arecibo", Geophysical Research Letters. Vol. 37, pp. L11103.
Abstract: All-sky imaging data of 630.0 nm airglow emissions are used to study the seasonal and solar activity dependence of medium-scale traveling ionospheric disturbances (MSTIDs) over Arecibo, Puerto Rico (18.3° N, 66.7° W, 28° N mag lat). MSTIDs are typical F-region signatures at midlatitudes, yet limited statistical results in the American sector hindered the progress in our understanding of these dynamical structures. This study compiles data from 2002 to 2007 and shows for the first time that optically-determined MSTIDs at Arecibo present a semiannual pattern with peak occurrence at both solstices. In the Japanese longitude sector, a similar pattern has been found, but one with a main peak during local summer. This paper explains the high occurrence rate during local winter at Arecibo via E-layer/F-layer coupling and inter-hemispheric coupling, thus accounting for a consistent morphology between the two longitude sectors.
BibTeX:
@article{Martinis2010,
  author = {Martinis, C. and Baumgardner, J. and Wroten,J. and Mendillo, M.},
  title = {Seasonal dependence of MSTIDs obtained from 630.0 nm airglow imaging at Arecibo},
  journal = {Geophysical Research Letters},
  year = {2010},
  volume = {37},
  pages = {L11103},
  url = {http://dx.doi.org/10.1029/2010GL043569},
  doi = {10.1029/2010GL043569}
}
Mathews JD, Briczinski SJ, Malhotra A and Cross J (2010), "Extensive meteoroid fragmentation in V/UHF radar meteor observations at Arecibo Observatory", Geophysical Research Letters. Vol. 37(4), pp. n/a-n/a.
Abstract: New 46.8/430 MHz (V/UHF) radar meteor observations at Arecibo Observatory reveal many previously unreported features in the radar meteor return that are consistent with meteoroid fragmentation. These signature features—observed at both V/UHF—include strong intra-pulse and pulse-to-pulse fading as the result of interference between or among multiple meteor head-echo returns and between head-echo and impulsive “flare” event “trail-echoes”. A few events are suggestive of differential ablation. These V/UHF radar observations are particularly useful as coaxial beams enable common volume observations that remove much ambiguity in the interpretation of the observations in terms of meteoroid fragmentation. These results, combined with simple modeling and two 500 sample statistical studies, lead us to conclude that a majority of the ~17,000 AO radar meteor events included in this study exhibit fragmentation—manifested as non-uniform lightcurves—implying that the form of meteoroid mass flux into the upper atmosphere goes well beyond simple ablation.
BibTeX:
@article{Mathews2010,
  author = {Mathews, J. D. and Briczinski, S. J. and Malhotra, A. and Cross, J.},
  title = {Extensive meteoroid fragmentation in V/UHF radar meteor observations at Arecibo Observatory},
  journal = {Geophysical Research Letters},
  year = {2010},
  volume = {37},
  number = {4},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2009GL041967},
  doi = {10.1029/2009GL041967}
}
Matteo NA and Morton YT (2010), "Higher-order ionospheric error at Arecibo, Millstone, and Jicamarca", Radio Science. Vol. 45(6), pp. n/a-n/a.
Abstract: The ionosphere is a dominant source of Global Positioning System receiver range measurement error. Although dual-frequency receivers can eliminate the first-order ionospheric error, most second- and third-order errors remain in the range measurements. Higher-order ionospheric error is a function of both electron density distribution and the magnetic field vector along the GPS signal propagation path. This paper expands previous efforts by combining incoherent scatter radar (ISR) electron density measurements, the International Reference Ionosphere model, exponential decay extensions of electron densities, the International Geomagnetic Reference Field, and total electron content maps to compute higher-order error at ISRs in Arecibo, Puerto Rico; Jicamarca, Peru; and Millstone Hill, Massachusetts. Diurnal patterns, dependency on signal direction, seasonal variation, and geomagnetic activity dependency are analyzed. Higher-order error is largest at Arecibo with code phase maxima circa 7 cm for low-elevation southern signals. The maximum variation of the error over all angles of arrival is circa 8 cm.
BibTeX:
@article{Matteo2010,
  author = {Matteo, N. A. and Morton, Y. T.},
  title = {Higher-order ionospheric error at Arecibo, Millstone, and Jicamarca},
  journal = {Radio Science},
  year = {2010},
  volume = {45},
  number = {6},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2010RS004394},
  doi = {10.1029/2010RS004394}
}
Ratovsky K, Shpynev B, Oinats A and Medvedev A (2010), "An analysis of the topside ionosphere parameters based on the long-duration Irkutsk incoherent scatter radar measurements", Advances in Space Research. Vol. 46(8), pp. 984-989.
Abstract: The topside ionosphere parameters are studied based on the long-duration Irkutsk incoherent scatter radar (52.9N, 103.3E) measurements conducted in September 2005, June and December 2007. As a topside ionosphere parameter we chose the vertical scale height (VSH) related to the gradient of the electron density logarithm above the peak height. For morphological studies we used median electron density profiles. Besides the median behavior we also studied VSH disturbances (deviations from median values) during the magnetic storm of September 11th 2005. We compared the Irkutsk incoherent scatter radar data with the Millstone Hill and Arecibo incoherent scatter radar observations, the IRI-2007 prediction (using the two topside options) and VSH derived from the Irkutsk DPS-4 Digisonde bottomside measurements.
BibTeX:
@article{Ratovsky2010,
  author = {K.G. Ratovsky and B.G. Shpynev and A.V. Oinats and A.V. Medvedev},
  title = {An analysis of the topside ionosphere parameters based on the long-duration Irkutsk incoherent scatter radar measurements},
  journal = {Advances in Space Research},
  year = {2010},
  volume = {46},
  number = {8},
  pages = {984-989},
  doi = {10.1016/j.asr.2010.06.006}
}
Rother M, Schlegel K, Luhr H and Cooke D (2010), "Validation of CHAMP electron temperature measurements by incoherent scatter radar data", Radio Science. Vol. 45(6), pp. n/a-n/a.
Abstract: The CHAMP performed electron temperature, Te, measurements during its mission period from 2000 to 2010. For the validation of these Te data comparisons with incoherent scatter radar observations at Arecibo and Tromsø (EISCAT) have been performed. Data from 94 (143) close encounters of the satellite with the Arecibo (Tromsø) radar are available for the validation. Results at Tromsø were reasonable, but at Arecibo significant differences, in particular for low temperature, were observed. Investigations showed that CHAMP Te measurements have a bias which switches sign between northbound and southbound orbit arcs. The global distribution of the bias shows systematic latitudinal structures antisymmetric to the magnetic equator. After correction of this effect, CHAMP Te data show a good agreement with the radar observations at both sites. From the mean relative deviation we deduce that CHAMP Te data are low by 3% with a standard deviation of 8%. Validated CHAMP Te data are available for the period 20 February 2002 through 20 February 2010.
BibTeX:
@article{Rother2010,
  author = {Rother, M. and Schlegel, K. and Luhr, H. and Cooke, D.},
  title = {Validation of CHAMP electron temperature measurements by incoherent scatter radar data},
  journal = {Radio Science},
  year = {2010},
  volume = {45},
  number = {6},
  pages = {n/a-n/a},
  doi = {10.1029/2010RS004445}
}
Souza J, Brum CGM, Abdu M, Batista I, Jr. WA, Bailey G and Bittencourt J (2010), "Parameterized Regional Ionospheric Model and a comparison of its results with experimental data and IRI representations ", Advances in Space Research . Vol. 46(8), pp. 1032-1038.
Abstract: We describe a Parameterized Regional Ionospheric Model (PARIM) to calculate the spatial and temporal variations of the ionospheric electron density/plasma frequency over the Brazilian sector. The ionospheric plasma frequency values as calculated from an enhanced Sheffield University Plasmasphere–Ionosphere Model (SUPIM) were used to construct the model. PARIM is a time-independent 3D regional model (altitude, longitude/local time, latitude) used to reproduce SUPIM plasma frequencies for geomagnetic quiet condition, for any day of the year and for low to moderately high solar activity. The procedure to obtain the modeled representation uses finite Fourier series so that all plasma frequency dependencies can be represented by Fourier coefficients. PARIM presents very good results, except for the F region peak height (hmF2) near the geomagnetic equator during times of occurrence of the F3 layer. The plasma frequency calculated by IRI from E region to bottomside of the F region present latitudinal discontinuities during morning and evening times for both solar minimum and solar maximum conditions. Both the results of PARIM and the IRI for the E region peak density show excellent agreement with the observational values obtained during the conjugate point equatorial experiment (COPEX) campaign. The IRI representations significantly underestimate the foF2 and hmF2 compared to the observational results over the COPEX sites, mainly during the evening-nighttime period.
BibTeX:
@article{Souza2010,
  author = {J.R. Souza and C. G. M. Brum and M.A. Abdu and I.S. Batista and W.D. Asevedo Jr. and G.J. Bailey and J.A. Bittencourt},
  title = {Parameterized Regional Ionospheric Model and a comparison of its results with experimental data and IRI representations },
  journal = {Advances in Space Research },
  year = {2010},
  volume = {46},
  number = {8},
  pages = {1032-1038},
  note = {Arecibo author},
  url = {http://www.sciencedirect.com/science/article/pii/S0273117710003911},
  doi = {10.1016/j.asr.2009.11.025}
}
Colon AAA (2010), "Research Experience for Undergraduates Program, PROGRESS REPORT SUMMER 2010"
BibTeX:
@techreport{,
  author = {Angel A. Acosta Colon},
  title = {Research Experience for Undergraduates Program, PROGRESS REPORT SUMMER 2010},
  year = {2010}
}
Abdu MA and Brum CGM (2009), "Electrodynamics of the vertical coupling processes in the atmosphere-ionosphere system of the low latitude region", Earth Planets and Space. Vol. 61, pp. 385-395.
Abstract: Dynamical, electro-dynamical and electrical coupling processes originating from upward propagation of atmospheric waves, and magnetosphere-ionosphere interaction are responsible for the large degree of variabilities observed in the low latitude ionosphere. One of the most outstanding aspects of its phenomenology is related to the sunset electrodynamical processes responsible for the evening enhancements in zonal and vertical electric fields and the associated spread of F/plasma bubble irregularity development. Recent observational results have provided evidence of significant contribution to their quiet time variability arising from thermospheric wind patterns, upward propagating planetary waves and possibly sporadic E layers. This paper provides an overview and some new results on planetary wave coupling with the equatorial F region, the E layer conductivity as key connecting mechanism, a possibly interactive role by sporadic E layers, and the resulting day-to-day variability in the evening prereversal electric field enhancements with consequences on spread F development.
BibTeX:
@article{Abdu2009,
  author = {M. A. Abdu and C. G. M. Brum},
  title = {Electrodynamics of the vertical coupling processes in the atmosphere-ionosphere system of the low latitude region},
  journal = {Earth Planets and Space},
  year = {2009},
  volume = {61},
  pages = {385-395},
  note = {Arecibo author},
  url = {http://adsabs.harvard.edu/abs/2009EP%26S...61..385A}
}
Briczinski SJ, Mathews JD and Meisel DD (2009), "Statistical and fragmentation properties of the micrometeoroid flux observed at Arecibo", Journal of Geophysical Research: Space Physics. Vol. 114(A4), pp. n/a-n/a.
Abstract: The micrometeor observations performed using the 430 MHz Arecibo Observatory radar have proven to be crucial for the understanding of meteoric effects on the aeronomy of the upper atmosphere. Meteors observed during the February 2001, 2006, and 2007 campaigns have been analyzed with a fast Fourier transform periodic search algorithm that automatically and uniformly detects meteor events between altitudes of 80 and 142 km. We present a description of the new technique used to detect meteors as well as the meteoroid parameters: altitude profiles, radial speeds, and decelerations. We also note the expected correlation between the radar transmitted power and the observed meteor event rate. The large number of events has enabled us to statistically estimate the average mass density of the observed population indicating that our detected events are generally cometary (1 g/cm3) and not asteroidal (3 g/cm3) in origin. Additionally, many meteor events are observed in which the radar meteor disappears from one radar pulse to the next (i.e., in 1 ms). We interpret this as indicative of the catastrophic destruction of the meteoroid. Until destruction, these events appear to undergo only minor ablation of their volatile components over the observed trajectory. As with a major fraction of all events recorded, the meteoroids that disappear in a terminal event show linear decelerations before their abrupt disappearance. This apparently low ablative mass deposition process may play an important role in the composition (aeronomy) of the upper atmosphere, as it likely produces submicron-sized particles rather than the atom level products of ablation. First results on the altitude, speed, and mass distributions of terminal event meteoroids are given yielding some clues on the physics of the terminal event. Finally, the statistics of those events that yield no deceleration are compared statistically with those that exhibit deceleration with the conclusion that both groups are statistically the same. We further conclude that along with low signal-to-noise ratio and short echo duration, fragmentation of this group of particles is a primary cause of the inability to determine deceleration.
BibTeX:
@article{Briczinski2009,
  author = {Briczinski, S. J. and Mathews, J. D. and Meisel, D. D.},
  title = {Statistical and fragmentation properties of the micrometeoroid flux observed at Arecibo},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2009},
  volume = {114},
  number = {A4},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2009JA014054},
  doi = {10.1029/2009JA014054}
}
Christakis N, Haldoupis C, Zhou Q and Meek C (2009), "Seasonal variability and descent of mid-latitude sporadic E layers at Arecibo", Annales Geophysicae. Vol. 27, pp. 923-931.
Abstract: Sporadic E layers (Es) follow regular daily patterns in variability and altitude descent, which are determined primarily by the vertical tidal wind shears in the lower thermosphere. In the present study a large set of sporadic E layer incoherent scatter radar (ISR) measurements are analyzed. These were made at Arecibo (Geog. Lat. ~18° N; Magnetic Dip ~50°) over many years with ISR runs lasting from several hours to several days, covering evenly all seasons. A new methodology is applied, in which both weak and strong layers are clearly traced by using the vertical electron density gradient as a function of altitude and time. Taking a time base equal to the 24-h local day, statistics were obtained on the seasonal behavior of the diurnal and semidiurnal tidal variability and altitude descent patterns of sporadic E at Arecibo. The diurnal tide, most likely the S(1,1) tide with a vertical wavelength around 25 km, controls fully the formation and descent of the metallic Es layers at low altitudes below 110 km. At higher altitudes, there are two prevailing layers formed presumably by vertical wind shears associated mainly with semidiurnal tides. These include: 1) a daytime layer starting at ~130 km around midday and descending down to 105 km by local midnight, and 2) a less frequent and weaker nighttime layer which starts prior to midnight at ~130 km, descending downwards at somewhat faster rate to reach 110 km by sunrise. The diurnal and semidiurnal-like pattern prevails, with some differences, in all seasons. The differences in occurrence, strength and descending speeds between the daytime and nighttime upper layers are not well understood from the present data alone and require further study.
BibTeX:
@article{Christakis2009,
  author = {Christakis, N and Haldoupis, C and Zhou, Q and Meek, C},
  title = {Seasonal variability and descent of mid-latitude sporadic E layers at Arecibo},
  journal = {Annales Geophysicae},
  year = {2009},
  volume = {27},
  pages = {923-931},
  url = {www.ann-geophys.net/27/923/2009/},
  doi = {10.5194/angeo-27-923-2009}
}
Fentzke J, Janches D and Sparks J (2009), "Latitudinal and seasonal variability of the micrometeor input function: A study using model predictions and observations from Arecibo and PFISR", Journal of Atmospheric and Solar-Terrestrial Physics. Vol. 71, pp. 653-661.
Abstract: In this work, we use a semi-empirical model of the micrometeor input function (MIF) together with meteor head-echo observations obtained with two high power and large aperture (HPLA) radars, the 430 MHz Arecibo Observatory (AO) radar in Puerto Rico (18°N, 67°W) and the 450 MHz Poker flat incoherent scatter radar (PFISR) in Alaska (65°N, 147°W), to study the seasonal and geographical dependence of the meteoric flux in the upper atmosphere. The model, recently developed by Janches et al. [2006a. Modeling the global micrometeor input function in the upper atmosphere observed by high power and large aperture radars. Journal of Geophysical Research 111] and Fentzke and Janches [2008. A semi-empirical model of the contribution from sporadic meteoroid sources on the meteor input function observed at arecibo. Journal of Geophysical Research (Space Physics) 113 (A03304)], includes an initial mass flux that is provided by the six known meteor sources (i.e. orbital families of dust) as well as detailed modeling of meteoroid atmospheric entry and ablation physics. In addition, we use a simple ionization model to treat radar sensitivity issues by defining minimum electron volume density production thresholds required in the meteor head-echo plasma for detection. This simplified approach works well because we use observations from two radars with similar frequencies, but different sensitivities and locations. This methodology allows us to explore the initial input of particles and how it manifests in different parts of the MLT as observed by these instruments without the need to invoke more sophisticated plasma models, which are under current development. The comparisons between model predictions and radar observations show excellent agreement between diurnal, seasonal, and latitudinal variability of the detected meteor rate and radial velocity distributions, allowing us to understand how individual meteoroid populations contribute to the overall flux at a particular location and season.
BibTeX:
@article{Fentzke2009,
  author = {J.T. Fentzke and D. Janches and J.J. Sparks},
  title = {Latitudinal and seasonal variability of the micrometeor input function: A study using model predictions and observations from Arecibo and PFISR},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
  year = {2009},
  volume = {71},
  pages = {653-661},
  doi = {10.1016/j.jastp.2008.07.015}
}
Fentzke J, Janches D, Strelnikova I and Rapp M (2009), "Meteoric smoke particle properties derived using dual-beam Arecibo UHF observations of D-region spectra during different seasons", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 71(17-18), pp. 1982-1991.
Abstract: We present a seasonal study of the presence and characteristics of meteoric smoke particles (MSPs) in the D-region plasma derived from observations using the Gregorian and line feeds of the 430 MHz dual-beam Arecibo Observatory (AO) incoherent scatter radar (ISR) in Puerto Rico (18?N,67?W)(18?N,67?W). MSPs are the product of re-condensation of ablated meteoric material and are believed to be the condensation nuclei for the formation of ice particles in the polar mesopause region. These CNs can then be responsible for the formation of polar mesospheric clouds (PMCs), noctilucent clouds (NLCs) and polar mesospheric summer echoes (PMSEs). For this work, we simultaneously employed both AO antenna feeds to define two radar beams inclined 15?15? east and west of zenith (Janches et al., 2006). Because of the non-vertical pointing, the sampled spectra are Doppler shifted due to the rapidly changing neutral dynamics of the MLT region. We correct this effect by removing the Doppler shift using the radial velocities estimated every ?2?2 min and then integrate the corrected spectra for longer periods to enhance signal-to-noise ratio (SNR) and better investigate the variability of MSP properties. We determine MSP radii and number densities utilizing a method similar to the one developed by Strelnikova et al. (2007) in which the autocorrelation function (ACF) is approximated as the sum of two exponential decays, i.e., the power spectrum is approximated as the sum of two Lorentzians. This method, which assumes mono-disperse particles, allows us to determine mean particle properties in the 80–95 km altitude range during the hours of 10–14 AO LT when the detected SNR from the D-region is highest. Results from this work show MSP radii approximately 0.6–1.5 nm is size depending on altitude and season. Also, MSP densities as a function of altitude and season are determined with the aid of the IRI model resulting in values on the order of 102–104102–104 per cubic centimeter. Our error analysis shows that spectral broadening from atmospheric sources such as neutral turbulence induced by gravity wave vertical variance, and non-zero vertical winds results in <10%<10% change in derived MSP radii. Also, since our dataset covers different seasons, we investigate a potential correlation between the seasonal variations of the derived MSPs properties with that of the meteoric input function (MIF) in the MLT above Arecibo.
BibTeX:
@article{Fentzke2009a,
  author = {J.T. Fentzke and D. Janches and I. Strelnikova and M. Rapp},
  title = {Meteoric smoke particle properties derived using dual-beam Arecibo UHF observations of D-region spectra during different seasons},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2009},
  volume = {71},
  number = {17-18},
  pages = {1982-1991},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682609002326},
  doi = {10.1016/j.jastp.2009.09.002}
}
Friedman JS, Zhang X, Chu X and Forbes JM (2009), "Longitude variations of the solar semidiurnal tides in the mesosphere and lower thermosphere at low latitudes observed from ground and space", Journal of Geophysical Research: Atmospheres. Vol. 114(D11), pp. n/a-n/a.
Abstract: We present an analysis of longitudinal variation in the solar semidiurnal tide observed in the nocturnal thermal structure of the low-latitude mesopause region (83–103 km), with a focus on two sites: Arecibo, Puerto Rico (18.3°N, 66.8°W) and Maui, Hawaii (20.7°N, 156.3°W). Localized observations made by lidars are combined with longitudinal measurements by Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) and compared with the Global-Scale Wave Model-2002 (GSWM-02) for 6 months: January, April, May, July, August, and October. In winter-spring, lidar-measured amplitudes are larger than those recorded by SABER, whereas in summer the amplitudes are similar and in autumn the lidars observe smaller amplitudes than SABER. GSWM amplitudes are between the lidar and SABER measurements for January, are comparable to the measurements in spring, underpredict for summer, and agree with the lidars in autumn. The phase structure is consistent among lidars and SABER for all of the months except January, when there is a large phase shift, and the local time of the temperature maximum is different between Arecibo and Maui. GSWM shows better agreement with phase measurements in winter-spring than in summer-autumn. Modal analysis of the SABER data indicates that the (2, 2) Hough mode is present throughout the year. In winter, it is joined by the (2, 4) mode, while in summer it is accompanied by the (2, 3) mode. This change in the predominant Hough modes may be related to the winter-summer phase difference.
BibTeX:
@article{Friedman2009,
  author = {Friedman, Jonathan S. and Zhang, Xiaoli and Chu, Xinzhao and Forbes, Jeffrey M.},
  title = {Longitude variations of the solar semidiurnal tides in the mesosphere and lower thermosphere at low latitudes observed from ground and space},
  journal = {Journal of Geophysical Research: Atmospheres},
  year = {2009},
  volume = {114},
  number = {D11},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2009JD011763},
  doi = {10.1029/2009JD011763}
}
Huang W, Chu X, Wiig J, Tan B, Yamashita C, Yuan T, Yue J, Harrell SD, She C-Y, Williams BP, Friedman JS and Hardesty RM (2009), "Field demonstration of simultaneous wind and temperature measurements from 5to50 km with a Na double-edge magneto-optic filter in a multi-frequency Doppler lidar", Optics Letters., May, 2009. Vol. 34(10), pp. 1552-1554. OSA.
Abstract: We report the first (to our knowledge) field demonstration of simultaneous wind and temperature measurements with a Na double-edge magneto-optic filter implemented in the receiver of a three-frequency Na Doppler lidar. Reliable winds and temperatures were obtained in the altitude range of 10-45 km with 1 km resolution and 60 min integration under the conditions of 0.4 W lidar power and 75 cm telescope aperture. This edge filter with a multi-frequency lidar concept can be applied to other direct-detection Doppler lidars for profiling both wind and temperature simultaneously from the lower to the upper atmosphere.
BibTeX:
@article{Huang:09,
  author = {Wentao Huang and Xinzhao Chu and Johannes Wiig and Bo Tan and Chihoko Yamashita and T. Yuan and J. Yue and S. D. Harrell and C.-Y. She and B. P. Williams and J. S. Friedman and R. M. Hardesty},
  title = {Field demonstration of simultaneous wind and temperature measurements from 5to50 km with a Na double-edge magneto-optic filter in a multi-frequency Doppler lidar},
  journal = {Optics Letters},
  publisher = {OSA},
  year = {2009},
  volume = {34},
  number = {10},
  pages = {1552--1554},
  url = {http://ol.osa.org/abstract.cfm?URI=ol-34-10-1552},
  doi = {10.1364/OL.34.001552}
}
Hysell DL, Nossa E, Larsen MF, Munro J, Sulzer MP and Gonzalez SA (2009), "Sporadic E layer observations over Arecibo using coherent and incoherent scatter radar: Assessing dynamic stability in the lower thermosphere", Journal of Geophysical Research: Space Physics. Vol. 114(A12), pp. n/a-n/a.
Abstract: A patchy sporadic E ionization layer was observed using the 430 MHz incoherent scatter radar at the Arecibo Radio Observatory and a new, 30 MHz coherent scatter radar imager located on St. Croix. The former measured state parameters of the layer (plasma density, temperature, and composition) while the latter observed small-scale plasma waves and the associated quasiperiodic (QP) echoes. Regularization was used to estimate horizontal vector ion drifts from Arecibo line-of-sight data. Assuming the ion temperatures and drifts to be representative of the neutral atmospheric temperatures and drifts in the mesosphere lower-thermosphere (MLT) region, we evaluated the Richardson number criterion for neutral dynamic instability in regions occupied by the layers. We find that the condition for instability was generally satisfied and thus that dynamic instability is consistent with the layer breakup. The electrodynamics of the resulting patchy layers could then give rise to the QP echoes.
BibTeX:
@article{Hysell2009,
  author = {Hysell, D. L. and Nossa, E. and Larsen, M. F. and Munro, J. and Sulzer, M. P. and Gonzalez, S. A.},
  title = {Sporadic E layer observations over Arecibo using coherent and incoherent scatter radar: Assessing dynamic stability in the lower thermosphere},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2009},
  volume = {114},
  number = {A12},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2009JA014403},
  doi = {10.1029/2009JA014403}
}
Janches D, Fritts D, Nicolls M and Heinselman C (2009), "Observations of D-region structure and atmospheric tides with PFISR during active aurora", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 71(6-7), pp. 688-696.
Abstract: We report on combined spectral measurements of the D-region ionosphere and the polar summer mesosphere and lower thermosphere performed on 9 June 2007 with the 450 MHz Poker Flat Incoherent Scatter Radar (PFISR) under active auroral conditions. Observations during the first 7 h occurred at nighttime and revealed strong temporal correlations between enhanced auroral precipitation, the occurrence of polar mesosphere summer echoes (PMSE), and enhanced electron densities (Ne) extending to much lower altitudes (~60-80km) than the previously reported at these latitudes without the presence of a polar cap absorption (PCA) event. PMSE and lower D-region echoes most often occurred together and PMSE were more often visible to PFISR before the Ne of the D-region was sufficiently high to be detected. These measurements also enabled definition of high precision horizontal winds (errors of 2–3ms-1) in the ~64–90km altitude range, which has previously been possible only with MF and HF radars, with the Arecibo 430 MHz IS radar (ISR), or with other ISRs during PCA events. This observing technique allowed for ~24h of almost continuous measurements of the meridional and zonal wind fields and thus permitted the measurements of atmospheric tides over this large altitude range. We determine amplitude and phase for both the diurnal and semi-diurnal tides showing the latter to be stronger as expected at these latitudes. We also present observations of a gravity wave during a quiet period indicating that PFISRs sensitivity is sufficiently high to obtain reliable spectral information even when electron densities are not enhanced by aurora or a PCA event and are as low as 109e-/m3. These results show the capabilities of PFISR to study the neutral dynamics in the polar D-region and mesosphere and lower thermosphere (MLT) over an unprecedented altitude range.
BibTeX:
@article{Janches2009,
  author = {D. Janches and D.C. Fritts and M.J. Nicolls and C.J. Heinselman},
  title = {Observations of D-region structure and atmospheric tides with PFISR during active aurora},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2009},
  volume = {71},
  number = {6-7},
  pages = {688-696},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682608002216},
  doi = {10.1016/j.jastp.2008.08.015}
}
Kelley MC, Wong VK, Aponte N, Coker C, Mannucci AJ and Komjathy A (2009), "Comparison of COSMIC occultation-based electron density profiles and TIP observations with Arecibo incoherent scatter radar data", Radio Science. Vol. 44(4), pp. n/a-n/a.
Abstract: In June 2006 an early opportunity arose to compare occultation-based electron density profiles with incoherent scatter radar data. The former were made available by the constellation of satellites called COSMIC. We find that the value of the peak plasma density in the F region is reasonably well characterized but that the altitude of the peak is overestimated above about 300 km and underestimated below that height. A simple Abel transform is not suitable for determining the E region profiles, even in daytime. We also compared the emission strength recorded by the Tiny Ionospheric Photometer (TIP) on board COSMIC to the Arecibo measurement of the TEC as part of an ongoing effort to calibrate the former. The TIP and Arecibo data both show the development of an ionospheric storm of the type referred to as high-intensity, long-duration continuous AE activity. It is surprising that such a modest magnetic storm (Dst ~-2.5 nT) resulted in the anomaly moving to nearly 30° magnetic latitude.
BibTeX:
@article{Kelley2009,
  author = {Kelley, M. C. and Wong, V. K. and Aponte, Nestor and Coker, Clayton and Mannucci, A. J. and Komjathy, A.},
  title = {Comparison of COSMIC occultation-based electron density profiles and TIP observations with Arecibo incoherent scatter radar data},
  journal = {Radio Science},
  year = {2009},
  volume = {44},
  number = {4},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2008RS004087},
  doi = {10.1029/2008RS004087}
}
Kelley MC, Ilma RR and Crowley G (2009), "On the origin of pre-reversal enhancement of the zonal equatorial electric field", Annales Geophysicae. Vol. 27, pp. 2053-2056.
Abstract: In November 2004, a large and variable interplanetary electric field (IEF) was felt in the reference frame of the Earth. This electric field penetrated to the magnetic equator and, when the Jicamarca Radio Observatory (JRO) was in the dusk sector, resulted in a reversal of the normal zonal component of the field. In turn, this caused a counter-electrojet (CEJ), a westward current rather than the usual eastward current. At the time of the normal pre-reversal enhancement (PRE) of the eastward field, the Jicamarca incoherent scatter radar (ISR) observed that the westward component became even more westward. Two of the three current explanations for the PRE depend on the neutral wind patterns. However, this unique event was such that the neutral wind-driven dynamos could not have changed. The implication is that the Haerendel-Eccles mechanism, which involves partial closure of the equatorial electrojet (EEJ) after sunset, must be the dominant mechanism for the PRE.
BibTeX:
@article{Kelley2009a,
  author = {Kelley, M C and Ilma, R R and Crowley, G},
  title = {On the origin of pre-reversal enhancement of the zonal equatorial electric field},
  journal = {Annales Geophysicae},
  year = {2009},
  volume = {27},
  pages = {2053-2056},
  doi = {10.5194/angeo-27-2053-2009}
}
Kelley MC and Dao E (2009), "On the local time dependence of the penetration of solar wind-induced electric fields to the magnetic equator", Annales Geophysicae. Vol. 27(8), pp. 3027-3030.
Abstract: For a period of a few hours, the penetration of electric fields of solar wind origin is at its highest efficiency. In November 2003, five days of continuous vertical drift data were obtained at the Jicamarca Radio Observatory. Here we have isolated a range of frequencies centered at a few-hour period for a five-day period and have explored the local time dependence of the penetration, along with the time delay due to magnetospheric effects. We find that the latter ranges from 15 to 25 min. For the local time dependence, we find that the period of anti-correlation is roughly from 21:00 to 04:00 LT, with positive correlation at other local times.
BibTeX:
@article{Kelley2009b,
  author = {Kelley, M. C. and Dao, E.},
  title = {On the local time dependence of the penetration of solar wind-induced electric fields to the magnetic equator},
  journal = {Annales Geophysicae},
  year = {2009},
  volume = {27},
  number = {8},
  pages = {3027-3030},
  doi = {10.5194/angeo-27-3027-2009}
}
Krall J, Huba JD and Martinis CR (2009), "Three-dimensional modeling of equatorial spread F airglow enhancements", Geophysical Research Letters. Vol. 36(10), pp. n/a-n/a.
Abstract: A sequence of 630.0 nm images obtained with the Boston University all-sky imaging system at Arecibo (18.3 N, 66.7 W, 28 N mag) shows equatorial spread F (ESF) airglow depletions evolving into ESF airglow enhancements. Using a combination of a meridional wind and a converging zonal wind, the NRL ionosphere model SAMI3/ESF can reproduce ESF airglow enhancements.
BibTeX:
@article{Krall2009,
  author = {Krall, J. and Huba, J. D. and Martinis, C. R.},
  title = {Three-dimensional modeling of equatorial spread F airglow enhancements},
  journal = {Geophysical Research Letters},
  year = {2009},
  volume = {36},
  number = {10},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2009GL038441},
  doi = {10.1029/2009GL038441}
}
Larsen MF and Fesen CG (2009), "Accuracy issues of the existing thermospheric wind models: can we rely on them in seeking solutions to wind-driven problems?", Annales Geophysicae. Vol. 27(6), pp. 2277-2284.
Abstract: We address the question of the ability of empirical and general circulation model neutral wind profiles in the lower thermosphere to reproduce the observed characteristics of the winds in that part of the atmosphere. The winds in that altitude range are critical for electrodynamic processes, but evaluations of the model winds are generally difficult because of the sparse observational data, which makes an evaluation of the wind predictions over large areas difficult or impossible. In this paper, we use a recently identified characteristic of the winds in the lower thermosphere, namely the enhanced winds and strong shears between 95 and 115 km altitude, as a test of the models, at least in a statistical sense. Our results show that the Horizontal Wind Model (HWM) significantly underestimates the maximum winds and shears in the lower thermosphere, although it has reasonable agreement with the average winds. The NCAR general circulation model used in this study also underestimates the maximum winds and shears significantly when run with standard resolution, as well as producing an unrealistic increase of the wind speed with height. The agreement between the model and the observations improves significantly however, in a statistical sense, when the altitude resolution is increased. The improved height resolution in the model appears to produce a greater improvement in the model predictions than any of the other factors that we examined, such as improving the geomagnetic forcing or the forcing at the lower boundary.
BibTeX:
@article{Larsen2009,
  author = {Larsen, M. F. and Fesen, C. G.},
  title = {Accuracy issues of the existing thermospheric wind models: can we rely on them in seeking solutions to wind-driven problems?},
  journal = {Annales Geophysicae},
  year = {2009},
  volume = {27},
  number = {6},
  pages = {2277-2284},
  doi = {10.5194/angeo-27-2277-2009}
}
Leonovich LA and Taschilin AV (2009), "Aeronomic effects of the solar flares in the topside ionosphere", Earth, Planets and Space. Vol. 61(5), pp. 643-648.
Abstract: We obtained that according to the GPS data at altitudes of the topside ionosphere (h >300 km) a flare is able to cause a decrease of the electron content. Using the theoretical model it is shown that the intense transport of O+ ions into the above-situated plasma caused by a sharp increase in the ion production rate and thermal expansion of the ionospheric plasma is a cause of the formation of the negative disturbance in the electron concentration in the topside ionosphere.
BibTeX:
@article{Leonovich2009,
  author = {Leonovich, L. A. and Taschilin, A. V.},
  title = {Aeronomic effects of the solar flares in the topside ionosphere},
  journal = {Earth, Planets and Space},
  year = {2009},
  volume = {61},
  number = {5},
  pages = {643--648},
  url = {http://dx.doi.org/10.1186/BF03352941},
  doi = {10.1186/BF03352941}
}
Livneh DJ, Seker I, Djuth FT and Mathews JD (2009), "Omnipresent vertically coherent fluctuations in the ionosphere with a possible worldwide-midlatitude extent", Journal of Geophysical Research: Space Physics. Vol. 114(A6), pp. n/a-n/a.
Abstract: Incoherent Scatter Radar power profile observations at Arecibo, Millstone Hill, and the Poker Flat AMISR have revealed the continuous presence of Coherent Omnipresent Fluctuations in the Ionosphere (COFIs) with periods ranging from roughly 30 to 60 minutes and apparent vertical wavelengths increasing with altitude from tens to hundreds of kilometers. Upon high-pass filtering of the Incoherent Scatter Radar power profile and electron concentration data, the COFIs are seen unambiguously and ubiquitously in Arecibo results from 22–23 March 2004, 5–6 June, 21–25 September, and 17–20 November 2005, as well as Millstone Hill results from 4 October to 4 November 2002. The COFIs are strong throughout the F region, often spanning altitudes of 160 km to above 500 km, and are detected day and night in the F2 layer. In fact, the COFIs are seen at every time and altitude that there is sufficient plasma to detect them. The COFIs are also observed at Poker Flat, although the poor signal-to-noise ratio over segments of the data makes it difficult to determine whether or not they are always present. The consistent detection of the COFIs, along with the longitudinal alignment and large latitudinal spread of the observation sites, suggests that these waves are always present over at least North America. This phenomenon appears to have been reported in Total Electron Concentration (TEC) maps of the ionosphere over much of North America Tsugawa et al. (2007b) as well as in airglow images from Arecibo and many other midlatitude sites around the world. These observations give us insight into the horizontal properties of the waves. While Medium-Scale Ionospheric Disturbances (MSTIDs) are generally associated with aurorally generated acoustic gravity waves, the properties of the COFIs may suggest otherwise. We present other possible source mechanisms, notably a possible link to oscillations in the solar wind and magnetosphere. We have observed consistent fluctuations with periods of about an hour observed in magnetic field measurements taken at geosynchronous altitudes by the Geostationary Operational Environmental Satellites (GOES)-10 and -12 satellites, which may be linked to the COFIs. We give corresponding solar wind results from ACE and discuss possible coupling mechanisms.
BibTeX:
@article{Livneh2009,
  author = {Livneh, Dorey J. and Seker, Ilgin and Djuth, Frank T. and Mathews, John D.},
  title = {Omnipresent vertically coherent fluctuations in the ionosphere with a possible worldwide-midlatitude extent},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2009},
  volume = {114},
  number = {A6},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2008JA013999},
  doi = {10.1029/2008JA013999}
}
Martinis C, Baumgardner J, Mendillo M, Su S-Y and Aponte N (2009), "Brightening of 630.0 nm equatorial spread-F airglow depletions", Journal of Geophysical Research: Space Physics. Vol. 114(A6), pp. n/a-n/a.
Abstract: Observations from the Boston University all-sky imaging system at Arecibo, Puerto Rico (18.3°N, 66.7°W, 28°N mag), show an unusual behavior of nighttime 630.0-nm airglow depletions. Associated with equatorial spread-F (ESF), these structures move eastward before reversing their motion and become airglow enhancements. Few other cases have been found, all during December solstices. For the case study presented here, data from the Arecibo incoherent scatter radar and the Republic of China Scientific Satellite (ROCSAT-1) provide supporting information. The radar shows that around local midnight the background zonal and meridional plasma motions reverse to westward and southward, respectively. ROCSAT-1 shows enhanced ion density, i.e., a low-latitude plasma blob, above the bright feature recorded by the all-sky imager, indicating a possible connection between both phenomena. Drifts parallel to the magnetic field are observed only in the region where the enhancement occurs. One possible interpretation of this change in the brightness of the depleted structure involves the influence of northward meridional winds and a reversal in the zonal drift motion, most likely caused by a zonal wind reversal.
BibTeX:
@article{Martinis2009,
  author = {Martinis, Carlos and Baumgardner, Jeffrey and Mendillo, Michael and Su, Shin-Yi and Aponte, Nestor},
  title = {Brightening of 630.0 nm equatorial spread-F airglow depletions},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2009},
  volume = {114},
  number = {A6},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2008JA013931},
  doi = {10.1029/2008JA013931}
}
Morton YT, Zhou Q and van Graas F (2009), "Assessment of second-order ionosphere error in GPS range observables using Arecibo incoherent scatter radar measurements", Radio Science. Vol. 44(1), pp. n/a-n/a.
Abstract: The second-order ionosphere error in GPS range measurements is determined by the electron densities and the geomagnetic field projection onto the GPS signal propagation direction along the GPS signal propagation path. It can be a delay or an advancement error. This paper presents the second-order error analysis based on an extensive collection of electron density profiles measured by the Arecibo incoherent scatter radar and geomagnetic field vectors generated using the International Geomagnetic Reference Field model. The results indicate that the 56–500 km altitude range contributes a maximum of ?1.1 cm for GPS L1 signals arriving from the zenith at Arecibo. For signals coming from the north and south at 10 degree elevation angles, the maximum errors are 0.9 cm and ?3.4 cm, respectively. The maximum of the mean values of the second-order error computed using the entire data set are ?0.55 cm, 0.48 cm, and ?1.74 cm for a signal arriving from the zenith, from the north at 10 degrees elevation, and from the south at 10 degrees elevation, respectively. The paper also discusses the diurnal patterns and geomagnetic activity dependency of the second-order error. Finally, the International Reference Ionosphere model is used to obtain an upper bound estimation of error contributions from the 500–2000 km altitude range.
BibTeX:
@article{Morton2009,
  author = {Morton, Yu T. and Zhou, Qihou and van Graas, Frank},
  title = {Assessment of second-order ionosphere error in GPS range observables using Arecibo incoherent scatter radar measurements},
  journal = {Radio Science},
  year = {2009},
  volume = {44},
  number = {1},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2008RS003888},
  doi = {10.1029/2008RS003888}
}
Muller H-R, Frisch P, Fields B and Zank G (2009), "The Heliosphere in Time", Space Science Reviews. Vol. 143(1-4), pp. 415-425.
Abstract: Because of the dynamic nature of the interstellar medium, the Sun should have encountered a variety of different interstellar environments in its lifetime. As the solar wind interacts with the surrounding interstellar medium to form a heliosphere, different heliosphere shapes, sizes, and particle contents result from the different environments. Some of the large possible interstellar parameter space (density, velocity, temperature) is explored here with the help of global heliosphere models, and the features in the resulting heliospheres are compared and discussed. The heliospheric size, expressed as distance of the nose of the heliopause to the Sun, is set by the solar wind-interstellar pressure balance, even for extreme cases. Other heliospheric boundary locations and neutral particle results correlate with the interstellar parameters as well. If the H0 clouds identified in the Millennium Arecibo survey are typical of clouds encountered by the Sun, then the Sun spends~99.4% of the time in warm low density ISM, where the typical upwind heliosphere radii are up to two orders of magnitude larger than at present.
BibTeX:
@article{Muller2009,
  author = {Muller, H.-R. and Frisch, P.C. and Fields, B.D. and Zank, G.P.},
  title = {The Heliosphere in Time},
  journal = {Space Science Reviews},
  year = {2009},
  volume = {143},
  number = {1-4},
  pages = {415-425},
  doi = {10.1007/s11214-008-9448-7}
}
Seker I, Livneh DJ and Mathews JD (2009), "A 3-D empirical model of F region Medium-Scale Traveling Ionospheric Disturbance bands using incoherent scatter radar and all-sky imaging at Arecibo", Journal of Geophysical Research: Space Physics. Vol. 114(A6), pp. n/a-n/a.
Abstract: Perhaps the most persistent and prominent of the midlatitude nighttime F region phenomena observed with all-sky imagers is the Medium-Scale Traveling Ionospheric Disturbances (MSTID) that occur when the geomagnetic activity is low. We introduce a simple empirical 3-D model of these bands, which was developed on the basis of an extension of results given by Seker et al. (2008). Seker et al. (2008) reported observational results on the 3-D geometry of MSTID structures found using combined incoherent scatter radar (ISR) and all-sky imager observations over the Arecibo Observatory in Puerto Rico. To confirm and further investigate these findings, a simple empirical 3-D model of nighttime MSTID bands is constructed. We show ISR and all-sky imager results derived from the model, compare them with the actual observations, and highlight the important findings. This model is intended to replicate both the azimuth-scanning ISR and the all-sky imager results and is especially useful in explaining how these complex structures appear in azimuth-scanning ISR results. In addition, confidence in the empirical model allows us to know what to expect from the theory (of MSTID) and to assess how well geomagnetically quiet, nighttime, midlatitude, F region electrodynamics models succeed. Furthermore, the technique described in the paper is not limited to F region or midlatitudes only; it could be applied to any other phenomenon which can be observed by both radar and imager.
BibTeX:
@article{Seker2009,
  author = {Seker, Ilgin and Livneh, Dorey J. and Mathews, John D.},
  title = {A 3-D empirical model of F region Medium-Scale Traveling Ionospheric Disturbance bands using incoherent scatter radar and all-sky imaging at Arecibo},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2009},
  volume = {114},
  number = {A6},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2008JA014019},
  doi = {10.1029/2008JA014019}
}
Sparks J, Janches D, Nicolls M and Heinselman C (2009), "Seasonal and diurnal variability of the meteor flux at high latitudes observed using PFISR", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 71, pp. 644-652.
Abstract: We report in this and a companion paper [Fentzke, J.T., Janches, D., Sparks, J.J., 2008. Latitudinal and seasonal variability of the micrometeor input function: A study using model predictions and observations from Arecibo and PFISR. Journal of Atmospheric and Solar-Terrestrial Physics, this issue, doi:10.1016/j.jastp.2008.07.015] a complete seasonal study of the micrometeor input function (MIF) at high latitudes using meteor head-echo radar observations performed with the Poker Flat Incoherent Scatter Radar (PFISR). This flux is responsible for a number of atmospheric phenomena; for example, it could be the source of meteoric smoke that is thought to act as condensation nuclei in the formation of ice particles in the polar mesosphere. The observations presented here were performed for full 24-h periods near the summer and winter solstices and spring and autumn equinoxes, times at which the seasonal variability of the MIF is predicted to be large at high latitudes [Janches, D., Heinselman, C.J., Chau, J.L., Chandran, A., Woodman, R., 2006. Modeling of the micrometeor input function in the upper atmosphere observed by High Power and Large Aperture Radars, JGR, 11, A07317, doi:10.1029/2006JA011628]. Precise altitude and radar instantaneous line-of-sight (radial) Doppler velocity information are obtained for each of the hundreds of events detected every day. We show that meteor rates, altitude, and radial velocity distributions have a large seasonal dependence. This seasonal variability can be explained by a change in the relative location of the meteoroid sources with respect to the observer. Our results show that the meteor flux into the upper atmosphere is strongly anisotropic and its characteristics must be accounted for when including this flux into models attempting to explain related aeronomical phenomena. In addition, the measured acceleration and received signal strength distribution do not seem to depend on season; which may suggest that these observed quantities do not have a strong dependence on entry angle.
BibTeX:
@article{Sparks2009,
  author = {J.J. Sparks and D. Janches and M.J. Nicolls and C.J. Heinselman},
  title = {Seasonal and diurnal variability of the meteor flux at high latitudes observed using PFISR},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2009},
  volume = {71},
  pages = {644-652},
  doi = {10.1016/j.jastp.2008.08.009}
}
Strelnikova I (2009), "Mesospheric Aerosol Particles: Evidence from Rocket and Radar Techniques". Thesis at: University of Rostock.
BibTeX:
@phdthesis{Strelnikova2009,
  author = {Irina Strelnikova},
  title = {Mesospheric Aerosol Particles: Evidence from Rocket and Radar Techniques},
  school = {University of Rostock},
  year = {2009},
  url = {http://www.iap-kborn.de/fileadmin/user_upload/MAIN-abteilung/optik/Forschung/Doktorarbeiten/Strelnikova-Diss-2009.pdf}
}
Swartz WE, Kelley MC and Aponte N (2009), "E- and F-region coupling between an intense sporadic E layer and a mesoscale traveling ionospheric disturbance", Annales Geophysicae. Vol. 27(6), pp. 2475-2482.
Abstract: Considerable controversy exists concerning the relative roles of the E- and F-regions in controlling irregularity formation in the mid-latitude ionosphere, largely because electric fields due to a plasma instability in one region may map to the other if the perpendicular scales are sufficiently large. In this paper we look at a particularly fortuitous data set in which both E- and F-region observations were made using incoherent scatter radar, GPS, lidar, and coherent scatter radar. In this event, a dense, patchy sporadic E layer was detected that exhibited type I (two-stream) coherent echoes while, at the same time, the F-layer plasma was highly structured with plasma drifts of hundreds of m/s. We examine this event in the context of a mesoscale traveling ionospheric disturbance. The data presentation will be followed by comparison with current theories for coupling between these two regions.
BibTeX:
@article{Swartz2009,
  author = {Swartz, W. E. and Kelley, M. C. and Aponte, N.},
  title = {E- and F-region coupling between an intense sporadic E layer and a mesoscale traveling ionospheric disturbance},
  journal = {Annales Geophysicae},
  year = {2009},
  volume = {27},
  number = {6},
  pages = {2475-2482},
  url = {http://www.ann-geophys.net/27/2475/2009/},
  doi = {10.5194/angeo-27-2475-2009}
}
Garzon DP and Brum CGM (2009), "Research Experience for Undergraduates Program, PROGRESS REPORT SUMMER 2009"
BibTeX:
@techreport{,
  author = {Garzon, Diana Prado and Brum, Christiano Garnett Marques},
  title = {Research Experience for Undergraduates Program, PROGRESS REPORT SUMMER 2009},
  year = {2009}
}
Abdu M, Brum C, Batista I, Sobral J, de Paula E and Souza J (2008), "Solar flux effects on equatorial ionization anomaly and total electron content over Brazil: Observational results versus IRI representations", Advances in Space Research . Vol. 42(4), pp. 617-625.
Abstract: The F layer critical frequency (foF2) as measured by Digisondes in the equatorial and low latitude locations in Brazil is analyzed to investigate the seasonal and solar flux controls of the intensity of the equatorial ionization anomaly (EIA) in the equinoctial month of March. The analysis also included the total electron content (TEC) as measured by a GPS receiver operated at the EIA crest location. The foF2 data set covered a period of large solar flux variation from 1996 to 2003, while the GPS TEC data was for a period in 2002-2003 when the solar flux parameter F10.7 underwent large variations, permitting in both cases an examination of the solar flux effects on these parameters. The seasonal variation pattern in TEC shows a maximum in equinoctial months and a minimum in June solstice, with similar variations for foF2. The solar flux dependence of the TEC is a maximum during equinoxes, especially for post-sunset TEC values at times when the latitudinal distribution is controlled by the equatorial evening plasma fountain processes. Significant variations with local time are found in the degree of solar flux dependence for both the TEC and EIA. The EIA intensity shows large dependence on F10.7 during post-sunset to midnight hours. These results are discussed in comparison with their corresponding IRI representations.
BibTeX:
@article{Abdu2008,
  author = {M.A. Abdu and C.G.M. Brum and I.S. Batista and J.H.A. Sobral and E.R. de Paula and J.R. Souza},
  title = {Solar flux effects on equatorial ionization anomaly and total electron content over Brazil: Observational results versus IRI representations},
  journal = {Advances in Space Research },
  year = {2008},
  volume = {42},
  number = {4},
  pages = {617-625},
  url = {http://www.sciencedirect.com/science/article/pii/S0273117708000999},
  doi = {10.1016/j.asr.2007.09.043}
}
Bhatt AN, Nicolls MJ, Sulzer MP and Kelley MC (2008), "Observations of Plasma Line Splitting in the Ionospheric Incoherent Scatter Spectrum", Physical Review Letters. Vol. 100, pp. 045005. American Physical Society.
Abstract: Wide-bandwidth ionospheric incoherent scatter (IS) spectra obtained using the Arecibo IS radar show the occurrence of a split in the plasma line (i.e., two plasma lines) when the plasma frequency is close to the second harmonic of the electron gyrofrequency. This split is predicted in the IS theory for a magnetized plasma, but observations have never been reported. Here we present the experimental results and theoretical calculations supporting the observations. These results may assist in understanding the behavior of Langmuir waves in the magnetized plasma and are a validation of what historically was a somewhat controversial aspect of the IS theory.
BibTeX:
@article{Bhatt2008,
  author = {Bhatt, Asti N. and Nicolls, Michael J. and Sulzer, Michael P. and Kelley, Michael C.},
  title = {Observations of Plasma Line Splitting in the Ionospheric Incoherent Scatter Spectrum},
  journal = {Physical Review Letters},
  publisher = {American Physical Society},
  year = {2008},
  volume = {100},
  pages = {045005},
  url = {http://link.aps.org/doi/10.1103/PhysRevLett.100.045005},
  doi = {10.1103/PhysRevLett.100.045005}
}
Dyrud L, Behnke R, Kepko E, Sulzer M and Zafke S (2008), "Ionospheric ULF oscillations driven from above Arecibo", Geophysical Research Letters. Vol. 35, pp. L14101.
Abstract: Understanding the coupling between the surface of the sun, the solar corona, the solar wind, the Earth's magnetosphere and ionosphere is a major focus of today's space research. Over 20 years ago, detailed observations of the ionospheric electron density at Arecibo revealed short period fluctuations (3 minutes), but their cause was never determined. Also, in the past 20 years a number of papers have reported observations of discrete (1–5 mHz) waves at persistent “magic frequencies” in magnetometer data and radar observations of ionospheric drift. Such observations have been generally interpreted as standing waves excited by magnetospheric cavity compressional modes. This assertion has been recently challenged by suggestions that these magic frequencies are not standing waves, but are due to inherent oscillations in the solar wind. Here we show that a subset of discrete 1.7 mHz oscillations in the solar wind plasma density are likely transmitted via a passive magnetospheric oscillation, and are observed as small amplitude (0.1%), discrete 1.7 mHz oscillations in the ionospheric plasma line using the extremely sensitive ionospheric measurements over Arecibo, Puerto Rico. We present over three hours of data using the electron plasma line component of the Arecibo radar incoherent scatter radar spectrum, solar wind number density from the WIND satellite, and magnetic field from the GOES satellite. This paper demonstrates a link between the solar wind and low latitude ionosphere.
BibTeX:
@article{Dyrud2008,
  author = {Dyrud, LP and Behnke, R and Kepko, EL and Sulzer, M and Zafke, S},
  title = {Ionospheric ULF oscillations driven from above Arecibo},
  journal = {Geophysical Research Letters},
  year = {2008},
  volume = {35},
  pages = {L14101},
  url = {http://dx.doi.org/10.1029/2008GL034073},
  doi = {10.1029/2008GL034073}
}
Dyrud L and Janches D (2008), "Modeling the meteor head echo using Arecibo radar observations", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 70(13), pp. 1621-1632.
Abstract: This paper reports results obtained using a combined set of models to determine meteoroid properties by comparing expected and observed meteor head-echo signal-to-noise ratio (SNR) and line-of-sight Doppler velocity as measured in high-power and large-aperture (HPLA) radar observations. For this task we model: (1) meteor ablation and ionization processes, (2) meteor head-echo radar cross-section (RCS), (3) the radar equation, and (4) the radar antenna gain pattern, together with an automated least-squares fitting procedure to estimate meteoroid and observation parameters (i.e. aspect angle, location within the radar beam, etc.). We compared our simulated results with 236 head-echo events observed using the Arecibo 430 MHz radar in Puerto Rico. We found good agreement between modeled and observed SNR versus meteor altitude profiles for a broad range of head-echo observations. We also find reasonable agreement between meteoroid mass distributions resulting from these models and estimated using dynamical arguments, with the dynamical mass generally resulting in lower values by about 1–2 orders of magnitude. A characteristic of our methodology is that we can trace back the original mass and velocity of the meteoroid “above” the atmosphere (?150 km altitude) required to produce the observed meteors. We find that, the original mass is required to be, on average, 1–2 orders of magnitude larger than that at the time of observation, and 3 orders of magnitude larger than estimated using dynamical equations. These results suggest that many meteor head echoes are observed towards the end of the particle's life, which has significant implications for the use of these observations for the determination of meteoroid properties. The automated fitting procedure is very sensitive to the antenna pattern, and therefore allows for precise estimates of the location of the meteoroid's trajectory within the Arecibo radar beam. The results indicate a noticeable, but weak, dependence between the distance of the particle's trajectory from the center of the beam (i.e. maximum gain) and the mass and velocity of the meteoroid. This suggests that the Arecibo radar is not particularly biased toward a specific velocity population of meteoroids (i.e. high velocity) as has been suggested in previous work.
BibTeX:
@article{Dyrud2008a,
  author = {Lars Dyrud and Diego Janches},
  title = {Modeling the meteor head echo using Arecibo radar observations},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2008},
  volume = {70},
  number = {13},
  pages = {1621-1632},
  doi = {10.1016/j.jastp.2008.06.016}
}
Fentzke JT and Janches D (2008), "A semi-empirical model of the contribution from sporadic meteoroid sources on the meteor input function in the MLT observed at Arecibo", Journal of Geophysical Research: Space Physics. Vol. 113(A3), pp. n/a-n/a.
Abstract: In this paper, we present a modeling and observational study of the micrometeor input function with a focus on understanding how each of the extraterrestrial sporadic meteoroid sources contributes to the observed meteoric flux in the Mesosphere and Lower Thermosphere (MLT) atmospheric region. For this purpose, we expand the model presented by Janches et al. (2006) using a Monte Carlo technique and incorporating: 1) a widely accepted global mass flux, which is divided into different proportions among the known sporadic meteoroid sources as the initial input above Earth’s atmosphere; 2) contemporary knowledge on the source's velocity and radiant distributions; and 3) the full integration of the canonical meteor equations that describe the meteoroid entry and ablation physics. In addition, we constrain the initial input through a comparison of our modeled results with meteor observations obtained with the 430 MHz High Power and Large Aperture (HPLA) Arecibo radar in Puerto Rico that covers all seasons. The predicted meteor rates and velocity distributions are in excellent agreement with the observed ones without the need for any additional normalization factor. Our results indicate that although the Earth’s Apex centered radiant source, which is characterized by high geocentric speeds (?55 km/s), appears to be ?33% of the meteoroids in the Solar System at 1 AU, it accounts for ?60% of the meteors observed by the Arecibo HPLA radar in the atmosphere. The remaining 40% of observed meteors originate mostly from the Helion and Anti-Helion sources, with a very small, but constant during the day, contribution of the South and North Toroidal sources. These results also suggest that particles smaller than ?10?3?g with slow velocities (<30 km/s) will not significantly ablate and never become observable meteors. The motivation of this effort is to construct a new and more precise MIF model needed for the subsequent modeling of the atmospheric phenomena related to the meteoric flux.
BibTeX:
@article{Fentzke2008,
  author = {Fentzke, Jonathan T. and Janches, Diego},
  title = {A semi-empirical model of the contribution from sporadic meteoroid sources on the meteor input function in the MLT observed at Arecibo},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2008},
  volume = {113},
  number = {A3},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2007JA012531},
  doi = {10.1029/2007JA012531}
}
Friedrich M, Fankhauser M, Oyeyemi E and McKinnell LA (2008), "A neural network-based ionospheric model for Arecibo", Advances in Space Research. Vol. 42(4), pp. 776-781. Elsevier Science.
Abstract: The Arecibo Observatory (18°N, 66°W) has the world’s largest single dish antenna (300 m diameter). Beyond radio astronomy it can also operate as an incoherent scatter radar and in that mode its figure-of-merit makes it also one of the most powerful world-wide. For the present purpose all electron density data available on the web, from the beginning with the first erratic measurements in 1966 up to 2004 inclusive, were downloaded. The measurements range from about 100 km to beyond 700 km and are essentially evenly distributed, i.e. not dedicated to measure specific geophysical events. From manually edited/inspected data a neural network (NN) was established with season, hour of the day, solar activity and Kp as the input parameters. The performance of this model is checked against a – likewise NN based – global model of foF2, a measure of the maximum electron density of the ionosphere. Considering the diverse data sources and assumptions of the two models it can be concluded that they agree remarkably well.
BibTeX:
@article{Friedrich2008,
  author = {Friedrich, M and Fankhauser, M and Oyeyemi, E and McKinnell, L A},
  title = {A neural network-based ionospheric model for Arecibo},
  journal = {Advances in Space Research},
  publisher = {Elsevier Science},
  year = {2008},
  volume = {42},
  number = {4},
  pages = {776-781},
  doi = {10.1016/j.asr.2007.07.018}
}
Fritts DC and Janches D (2008), "Dual-beam measurements of gravity waves over Arecibo: Reevaluation of wave structure, dynamics, and momentum fluxes", Journal of Geophysical Research: Atmospheres. Vol. 113(D5), pp. n/a-n/a.
Abstract: A previous study by Zhou and Morton (2006) employed dual-beam incoherent scatter radar measurements of radial velocities at the Arecibo Observatory to study the structure, dynamics, and momentum fluxes of gravity waves in the mesosphere and lower thermosphere for ?8 h on 28 July 2001. Because of erroneous assumptions about wave character and inferences of the relationship between radial velocities, however, the advertised results of this previous study are largely in error. The purposes of the present study are both to point out these errors to help avoid such pitfalls in the future and to provide a new interpretation of these data, which represent a very interesting case study of gravity wave dynamics at these altitudes. Specific findings of the present study (largely in contradiction to the previous analysis) include (1) the ?15-min oscillation was apparently a large-amplitude Doppler-ducted gravity wave structure propagating at one or two maxima of the westward large-scale wind present during the event; (2) the gravity wave exhibited a deep and coherent vertical phase structure, except between the two westward wind maxima at later times, entirely inconsistent with proximity to a critical level; (3) the dominant motions within the gravity wavefield were vertical velocities up to ?10 m s–1, except for inferred horizontal motions where the vertical motions changed phase and above and below the vertical velocity maxima, as dictated by the continuity equation; (4) there were likely no regions of dynamical instability accompanying these ducted wave motions; and (5) momentum fluxes due to this wave motion were small, despite its very large amplitude.
BibTeX:
@article{Fritts2008,
  author = {Fritts, David C. and Janches, Diego},
  title = {Dual-beam measurements of gravity waves over Arecibo: Reevaluation of wave structure, dynamics, and momentum fluxes},
  journal = {Journal of Geophysical Research: Atmospheres},
  year = {2008},
  volume = {113},
  number = {D5},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2007JD008896},
  doi = {10.1029/2007JD008896}
}
Janches D, Close S and Fentzke JT (2008), "A comparison of detection sensitivity between ALTAIR and Arecibo meteor observations: Can high power and large aperture radars detect low velocity meteor head-echoes", Icarus. Vol. 193, pp. 105-111.
Abstract: Meteor head-echo observations using High Power and Large Aperture (HPLA) radars have been routinely used for micrometeor studies for over a decade. The head-echo is a signal from the radar-reflective plasma region traveling with the meteoroid and its detection allows for very precise determination of instantaneous meteor altitude, velocity and deceleration. Unlike specular meteor radars (SMR), HPLA radars are diverse instruments when compared one to another. The operating frequencies range from 46 MHz to 1.29 GHz while the antenna configurations changes from 18,000 dipoles in a 300 m×300 m300 m×300 m square array, phase arrays of dipoles to single spherical or parabolic dishes of various dimensions. Hunt et al. [Hunt, S.M., Oppenheim, M., Close, S., Brown, P.G., McKeen, F., Minardi, M., 2004. Icarus 168, 34–42] and Close et al. [Close, S., Brown, P., Campbell-Brown, M., Oppenheim, M., Colestock, P., 2007. Icarus, doi:10.1016/j.icarus.2006.09.07] recently showed, by utilizing a head-echo plasma-based model, the presence of instrumental biases in the ALTAIR VHF radar system against detecting meteors produced by very small particles (<1 ug) moving at slow (~20 km/s) velocities due to the low head echo radar cross-section (RCS) associated with these particles. In this paper we apply the same methodology to the Arecibo 430 MHz radar and compare the results with those presented by Close et al. [Close, S., Brown, P., Campbell-Brown, M., Oppenheim, M., Colestock, P., 2007. Icarus, doi:10.1016/j.icarus.2006.09.07]. We show that, if the methodology applied by Hunt et al. [Hunt, S.M., Oppenheim, M., Close, S., Brown, P.G., McKeen, F., Minardi, M., 2004. Icarus 168, 34–42] and Close et al. [Close, S., Brown, P., Campbell-Brown, M., Oppenheim, M., Colestock, P., 2007. Icarus, doi:10.1016/j.icarus.2006.09.07] is accurate, for particles at least 1 ug or heavier, while the bias may exist for the ALTAIR measurements, it does not exist in the Arecibo data due to its greater sensitivity.
BibTeX:
@article{Janches2008,
  author = {Janches, D and Close, S and Fentzke, J T},
  title = {A comparison of detection sensitivity between ALTAIR and Arecibo meteor observations: Can high power and large aperture radars detect low velocity meteor head-echoes},
  journal = {Icarus},
  year = {2008},
  volume = {193},
  pages = {105-111},
  url = {http://dx.doi.org/10.1016/j.icarus.2007.08.022},
  doi = {10.1016/j.icarus.2007.08.022}
}
Emmert JT, Drob DP, Shepherd GG, Hernandez G, Jarvis MJ, Meriwether JW, Niciejewski RJ, Sipler DP and Tepley CA (2008), "DWM07 global empirical model of upper thermospheric storm-induced disturbance winds", Journal of Geophysical Research: Space Physics. Vol. 113(A11), pp. n/a-n/a.
Abstract: We present a global empirical disturbance wind model (DWM07) that represents average geospace-storm-induced perturbations of upper thermospheric (200–600 km altitude) neutral winds. DWM07 depends on the following three parameters: magnetic latitude, magnetic local time, and the 3-h Kp geomagnetic activity index. The latitude and local time dependences are represented by vector spherical harmonic functions (up to degree 10 in latitude and order 3 in local time), and the Kp dependence is represented by quadratic B-splines. DWM07 is the storm time thermospheric component of the new Horizontal Wind Model (HWM07), which is described in a companion paper. DWM07 is based on data from the Wind Imaging Interferometer on board the Upper Atmosphere Research Satellite, the Wind and Temperature Spectrometer on board Dynamics Explorer 2, and seven ground-based Fabry-Perot interferometers. The perturbation winds derived from the three data sets are in good mutual agreement under most conditions, and the model captures most of the climatological variations evident in the data.
BibTeX:
@article{JGRA:JGRA19582,
  author = {Emmert, J. T. and Drob, D. P. and Shepherd, G. G. and Hernandez, G. and Jarvis, M. J. and Meriwether, J. W. and Niciejewski, R. J. and Sipler, D. P. and Tepley, C. A.},
  title = {DWM07 global empirical model of upper thermospheric storm-induced disturbance winds},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2008},
  volume = {113},
  number = {A11},
  pages = {n/a--n/a},
  url = {http://dx.doi.org/10.1029/2008JA013541},
  doi = {10.1029/2008JA013541}
}
Drob DP, Emmert JT, Crowley G, Picone JM, Shepherd GG, Skinner W, Hays P, Niciejewski RJ, Larsen M, She CY, Meriwether JW, Hernandez G, Jarvis MJ, Sipler DP, Tepley CA, O'Brien MS, Bowman JR, Wu Q, Murayama Y, Kawamura S, Reid IM and Vincent RA (2008), "An empirical model of the Earth's horizontal wind fields: HWM07", Journal of Geophysical Research: Space Physics. Vol. 113(A12), pp. n/a-n/a.
Abstract: The new Horizontal Wind Model (HWM07) provides a statistical representation of the horizontal wind fields of the Earth's atmosphere from the ground to the exosphere (0–500 km). It represents over 50 years of satellite, rocket, and ground-based wind measurements via a compact Fortran 90 subroutine. The computer model is a function of geographic location, altitude, day of the year, solar local time, and geomagnetic activity. It includes representations of the zonal mean circulation, stationary planetary waves, migrating tides, and the seasonal modulation thereof. HWM07 is composed of two components, a quiet time component for the background state described in this paper and a geomagnetic storm time component (DWM07) described in a companion paper.
BibTeX:
@article{JGRA:JGRA19649,
  author = {Drob, D. P. and Emmert, J. T. and Crowley, G. and Picone, J. M. and Shepherd, G. G. and Skinner, W. and Hays, P. and Niciejewski, R. J. and Larsen, M. and She, C. Y. and Meriwether, J. W. and Hernandez, G. and Jarvis, M. J. and Sipler, D. P. and Tepley, C. A. and O'Brien, M. S. and Bowman, J. R. and Wu, Q. and Murayama, Y. and Kawamura, S. and Reid, I. M. and Vincent, R. A.},
  title = {An empirical model of the Earth's horizontal wind fields: HWM07},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2008},
  volume = {113},
  number = {A12},
  pages = {n/a--n/a},
  url = {http://dx.doi.org/10.1029/2008JA013668},
  doi = {10.1029/2008JA013668}
}
Lee MC, Pradipta R, Burke WJ, Labno A, Burton LM, Cohen JA, Dorfman SE, Coster AJ, Sulzer MP and Kuo SP (2008), "Did Tsunami-Launched Gravity Waves Trigger Ionospheric Turbulence over Arecibo?", Journal of Geophysical Research: Space Physics. Vol. 113(A1), pp. n/a-n/a.
Abstract: We report on measurements of ionospheric plasma dynamics conducted at the Arecibo Observatory between 20:00 and 24:00 local time (LT) on December 25 and 26, 2004 using the 430 MHz incoherent scatter radar (ISR). For interpretive purposes these measurements are supported by data from two nearby ionosondes and Global Positioning System (GPS) satellites. The ISR detected different ionospheric behaviors during the vertical-transmission periods on the consecutive, magnetically quiet nights. On the night of December 25 the ionosphere descended smoothly and spread F signatures faded. For about two hours on the following evening the bottomside ionosphere rose by ~50 km, inducing plasma irregularities and intense spread F. Alternating cycles of bottom-side plasma rising and falling persisted through the remainder of the experiments. We postulate that this sinusoidal behavior is a response to gravity waves propagating above Puerto Rico. Nearly simultaneous data from two nearby stations show that GPS signals were modified by variations in total electron content (TEC) indicating the presence of traveling ionospheric disturbances (TIDs). The December 26 experiments were conducted about a day after an MW = 9.2 earthquake launched tsunami waves first across the Indian, then into the Atlantic and Pacific Oceans. We suggest that coupling at the tsunami sea-air interface launched gravity waves that propagated for great distances beneath the mesopause. GPS data recorded TEC variation in Asia, Europe, and the Caribbean, suggesting that TIDs were induced on a global scale at the wake of tsunami-launched gravity waves. Energy from imperfectly ducted gravity waves leaked into the ionosphere, partially over Puerto Rico. The wind-velocity field of these gravity waves caused local ionospheric plasma to rise, seeding bottomside irregularities via the generalized Rayleigh-Taylor instability.
BibTeX:
@article{Lee2008,
  author = {Lee, M. C. and Pradipta, R. and Burke, W. J. and Labno, A. and Burton, L. M. and Cohen, J. A. and Dorfman, S. E. and Coster, A. J. and Sulzer, M. P. and Kuo, S. P.},
  title = {Did Tsunami-Launched Gravity Waves Trigger Ionospheric Turbulence over Arecibo?},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2008},
  volume = {113},
  number = {A1},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2007JA012615},
  doi = {10.1029/2007JA012615}
}
Lee MC, Pradipta R, Burke WJ, Labno A, Burton LM, Cohen JA, Dorfman SE, Coster AJ, Sulzer MP and Kuo SP (2008), "Correction to Did tsunami-launched gravity waves trigger ionospheric turbulence over Arecibo?", Journal of Geophysical Research: Space Physics. Vol. 113(A0), pp. n/a-n/a.
BibTeX:
@article{Lee2008a,
  author = {Lee, M. C. and Pradipta, R. and Burke, W. J. and Labno, A. and Burton, L. M. and Cohen, J. A. and Dorfman, S. E. and Coster, A. J. and Sulzer, M. P. and Kuo, S. P.},
  title = {Correction to Did tsunami-launched gravity waves trigger ionospheric turbulence over Arecibo?},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2008},
  volume = {113},
  number = {A0},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2008JA013044},
  doi = {10.1029/2008JA013044}
}
Leonovich LA and Tashchilin AV (2008), "Disturbances in the topside ionosphere during solar flares", Geomagnetism and Aeronomy. Vol. 48, pp. 793-802.
Abstract: The results of studying the ionospheric response to solar flares, obtained from the data of the GPS signal observations and incoherent scatter radars and as a result of the model calculations, are presented. It is shown that, according to the GPS data, a flare can cause a decrease in the electron content at altitudes of the topside ionosphere (h > 300 km). Similar effects of formation of a negative disturbance in the ionospheric F region were also observed during the solar flares of May 21 and 23, 1967, with the Arecibo incoherent scatter radar. The mechanism by which negative disturbances appear in the topside ionosphere during solar flares has been studied in this work based on the theoretical model of the ionosphere-plasmasphere coupling. It has been indicated that the formation of the electron density negative disturbance in the topside ionosphere is caused by an intense removal of O+ ions into the overlying plasmasphere under the action of an abrupt increase in the ion production rate and thermal expansion of the ionospheric plasma.
BibTeX:
@article{Leonovich2008,
  author = {Leonovich, L A and Tashchilin, A V},
  title = {Disturbances in the topside ionosphere during solar flares},
  journal = {Geomagnetism and Aeronomy},
  year = {2008},
  volume = {48},
  pages = {793-802},
  url = {http://dx.doi.org/10.1134/S001679320806008X},
  doi = {10.1134/s001679320806008x}
}
Liu L, He M, Wan W and Zhang M-L (2008), "Topside ionospheric scale heights retrieved from Constellation Observing System for Meteorology, Ionosphere, and Climate radio occultation measurements", Journal of Geophysical Research: Space Physics. Vol. 113(A10), pp. n/a-n/a.
Abstract: The vertical scale height (VSH) in the topside ionosphere can be derived from electron density profiles. In this study, the electron density profiles retrieved from the COSMIC/FORMOSAT-3 (a Constellation Observing System for Meteorology, Ionosphere, and Climate mission; C/F3 for short) ionospheric radio occultation (IRO) observations have been collected to investigate the local time, seasonal, latitudinal, and longitudinal variations of the VSH. With the postprocessed C/F3 IRO electron density profiles during the interval from day of year (DOY) 194 in 2006 to DOY 60 in 2008, we conduct an analysis on the behaviors of VSH at an altitude of 400 km. There are appreciable latitudinal variations in VSH. A new finding is a significant peak around dip equator during daytime in four seasons. Away from the equatorial peak, it is obvious that the VSH generally increases at higher latitudes. The equatorial VSH undergoes a significant diurnal variation with a local noon maximum. The peak shifts to sunrise time with increasing dip latitude, and the values of daytime VSH become comparable with those at nighttime at low latitude in both hemispheres, which is somewhat different from the feature revealed from Arecibo incoherent scatter radar observations. One of the crucial findings in our results is the most outstanding feature of VSH, that is, the presence of a substantial longitudinal structure in equatorial regions. A wave-like longitudinal feature is found in equatorial VSH during the daytime in four seasons, while it becomes weaker or absent at other local time intervals and at higher latitudes. This investigation also confirms that the behaviors of VSH are not strongly consistent with those of the neutral or plasma-scale heights.
BibTeX:
@article{Liu2008,
  author = {Liu, Libo and He, Maosheng and Wan, Weixing and Zhang, Man-Lian},
  title = {Topside ionospheric scale heights retrieved from Constellation Observing System for Meteorology, Ionosphere, and Climate radio occultation measurements},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2008},
  volume = {113},
  number = {A10},
  pages = {n/a-n/a},
  doi = {10.1029/2008JA013490}
}
Liu G, Shepherd GG and Tepley CA (2008), "Variations of the tropical O(1S) nightglow as observed with the Arecibo Observatory photometer and WINDII on UARS", Journal of Atmospheric and Solar-Terrestrial Physics. Vol. 70(10), pp. 1309-1317.
Abstract: This work investigates the tropical O(1S) nightglow variations utilizing observations from the Wind Imaging Interferometer (WINDII) operated on the Upper Atmosphere Research Satellite (UARS) and photometers installed at the Arecibo Observatory (18°N, 67°W) in Puerto Rico. Both are long-term datasets, but there is limited overlap in the dates of observation. Their simultaneous observations of column integrated emission rate on 6 continuous days in 1993 have a consistent difference at some times. The ground-based emission rate includes the F-region component of the O(1S) emission, while the vertical profiles of WINDII allow the E- and F-region emission to be separated. This allows subtraction of the F-region emission rate for the Arecibo measurements and leads to a decisive study of the O(1S) nightglow variation. The monthly averaged integrated emission rates (excluding the F-region component) are computed for WINDII from November 1991 to August 1997 and for the photometer data through 1983–2004. The emission rates between WINDII and Arecibo exhibit a similar semiannual variation. They have maxima at the two equinoxes and minima at solstices with a larger maximum in spring than in fall, while the WINDII averaged emission rates are larger than the apparent photometer averages by a factor of 2 for the mean values. The satellite WINDII and ground-based Arecibo instruments sample local time hours differently, but the local time influence is found not to be the origin of the difference. Because the observation periods are for different solar cycle intervals for the WINDII and Arecibo datasets, the influence of the solar F10.7 cm flux on the O(1S) nightglow emission rate is also studied. The comparison between WINDII and Arecibo further offers a possibility to assess the atmospheric transmittance for these ground-based observations. The MODTRAN estimated transmittance of 0.7 is reasonably consistent with the difference in the O(1S) nightglow emission rate between WINDII and the Arecibo photometer.
BibTeX:
@article{Liu2008a,
  author = {Guiping Liu and Gordon G. Shepherd and Craig A. Tepley},
  title = {Variations of the tropical O(1S) nightglow as observed with the Arecibo Observatory photometer and WINDII on UARS},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
  year = {2008},
  volume = {70},
  number = {10},
  pages = {1309-1317},
  doi = {10.1016/j.jastp.2008.03.001}
}
Lu G, Goncharenko LP, Richmond AD, Roble RG and Aponte N (2008), "A dayside ionospheric positive storm phase driven by neutral winds", Journal of Geophysical Research: Space Physics. Vol. 113(A8), pp. A08304 (7 pages).
Abstract: This paper presents observations and numerical simulations of ionospheric and thermospheric disturbances associated with a moderate geomagnetic storm on 10 September 2005. During the event, the incoherent radars located in Millstone Hill and Arecibo observed a dayside positive storm phase as manifested by the enhanced electron density in the F region. The universal time (UT)-altitude profile of electron density measured by both radars displayed a structure that closely resembles the Greek letter A. A similar structure is also reproduced by the Thermosphere-Ionosphere Electrodynamics General Circulation Model (TIEGCM). This peculiar electron density distribution is found to be associated with vertical ion drift, which initially was upward and then became downward. Using realistic time-dependent ionospheric convection and auroral precipitation as inputs, the TIEGCM reveals that the primary cause of the positive storm response was the enhanced meridional neutral wind rather than the penetration magnetospheric electric field. This study reiterates the importance of neutral wind effects on ionospheric disturbance.
BibTeX:
@article{Lu2008,
  author = {Lu, G. and Goncharenko, L. P. and Richmond, A. D. and Roble, R. G. and Aponte, N.},
  title = {A dayside ionospheric positive storm phase driven by neutral winds},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2008},
  volume = {113},
  number = {A8},
  pages = {A08304 (7 pages)},
  url = {http://dx.doi.org/10.1029/2007JA012895},
  doi = {10.1029/2007JA012895}
}
Mathews J D and. Briczinski SJ, Meisel DD and Heinselman CJ (2008), "Radio and Meteor Science Outcomes From Comparisons of Meteor Radar Observations at AMISR Poker Flat, Sondrestrom, and Arecibo", Earth, Moon, and Planets. Vol. 102, pp. 365-372. Springer Netherlands.
Abstract: Radio science and meteor physics issues regarding meteor “head-echo” observations with high power, large aperture (HPLA) radars, include the frequency and latitude dependency of the observed meteor altitude, speed, and deceleration distributions. We address these issues via the first ever use and analysis of meteor observations from the Poker Flat AMISR (PFISR: 449.3 MHz), Sondrestrom (SRF: 1,290 MHz), and Arecibo (AO: 430 MHz) radars. The PFISR and SRF radars are located near the Arctic Circle while AO is in the tropics. The meteors observed at each radar were detected and analyzed using the same automated FFT periodic micrometeor searching algorithm. Meteor parameters (event altitude, velocity, and deceleration distributions) from all three facilities are compared revealing a clearly defined altitude “ceiling effect” in the 1,290 MHz results relative to the 430/449.3 MHz results. This effect is even more striking in that the Arecibo and PFISR distributions are similar even though the two radars are over 2,000 times different in sensitivity and at very different latitudes, thus providing the first statistical evidence that HPLA meteor radar observations are dominated by the incident wavelength, regardless of the other radar parameters. We also offer insights into the meteoroid fragmentation and “terminal” process.
BibTeX:
@article{Mathews2008,
  author = {Mathews, J D and. Briczinski, S J and Meisel, D D and Heinselman, C J},
  title = {Radio and Meteor Science Outcomes From Comparisons of Meteor Radar Observations at AMISR Poker Flat, Sondrestrom, and Arecibo},
  journal = {Earth, Moon, and Planets},
  publisher = {Springer Netherlands},
  year = {2008},
  volume = {102},
  pages = {365-372},
  doi = {10.1007/s11038-007-9168-0}
}
Mishin E and Milikh G (2008), "Blue Jets: Upward Lightning", Space Science Reviews. Vol. 137(1-4), pp. 473-488.
Abstract: Blue jets are beams of blue light propagating from the tops of active thunderclouds up to altitudes of ~50 km. They resemble tall trees with quasi-vertical trunk and filamentary branches. Their apparent speeds are in the range of 10 s to 100 s km/s. Other events, having essentially lower terminal altitudes (<26 km), are named blue starters. These phenomena represent the first documented class of upward electrical discharges in the stratosphere. Some of upward discharges, termed gigantic jets, propagate into the lower ionosphere at much higher speeds in the final phase. We describe salient features of the upward discharges in the atmosphere, give an assessment of the theories of their development, and discuss the consequences for the electrodynamics and chemistry of the stratosphere. We argue that this upward lightning phenomenon can be understood in terms of the bi-directional leader, emerging from the anvil.
BibTeX:
@article{Mishin2008,
  author = {Mishin, EvgenyV. and Milikh, GennadyM.},
  title = {Blue Jets: Upward Lightning},
  journal = {Space Science Reviews},
  year = {2008},
  volume = {137},
  number = {1-4},
  pages = {473-488},
  doi = {10.1007/s11214-008-9346-z}
}
Nikoukar R, Kamalabadi F, Kudeki E and Sulzer M (2008), "An efficient near-optimal approach to incoherent scatter radar parameter estimation", Radio Science. Vol. 43(5), pp. n/a-n/a.
Abstract: We present a computationally efficient, near-optimal approach to the estimation of ionospheric parameters from incoherent scatter radar measurements. The method consists of removing the range smearing of ionospheric autocorrelation function via a set of 1-D deconvolutions and performing nonlinear least squares fitting on the deconvolved autocorrelation functions. To stabilize the solution in the presence of noise, we incorporate regularization techniques. The computational cost is reduced significantly by estimating the ionospheric parameters at individual altitudes, in comparison to full-profile-type analysis, which attempts to estimate ionospheric parameters at all altitudes simultaneously. The performance of the new technique is evaluated in a numerical example and is shown to give estimates of almost equal quality as the full-profile technique but at a 95% reduction in computation.
BibTeX:
@article{Nikoukar2008,
  author = {Nikoukar, Romina and Kamalabadi, Farzad and Kudeki, Erhan and Sulzer, Michael},
  title = {An efficient near-optimal approach to incoherent scatter radar parameter estimation},
  journal = {Radio Science},
  year = {2008},
  volume = {43},
  number = {5},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2007RS003724},
  doi = {10.1029/2007RS003724}
}
Pradipta R, Cohen JA, Lee MC, Labno A, Burton LM, Riddolls RJ, Batishchev OV, Coster AJ, Burke WJ, Starks MJ, Sulzer MP and Kuo SP (2008), "Space plasma disturbances caused by NAU-launched whistler waves", Physica Scripta. Vol. T132, pp. 014031 (9pp).
Abstract: Radio signals from Naval (NAU) transmitter in Puerto Rico can interact effectively with naturally occurring or HF heater wave-induced large-scale ionospheric irregularities, allowing them to propagate as whistler-modes in the ionosphere and to the inner radiation belts. NAU-generated whistler-modes have intensities sufficient to parametrically excite lower hybrid waves and ten-meter and meter-scale ionospheric irregularities over Arecibo.
Subsequent heating of electrons and ions by the lower hybrid waves yield a sequence of ionospheric plasma effects such as airglow, short-scale density depletion and plasma line enhancements in a range of altitudes which far exceed that caused by the HF heater. Furthermore, they can interact with trapped energetic electrons in inner radiation belts at L = 1.35 and trigger precipitation of electrons into the lower ionosphere. We suggest that
disturbances in the ionosphere above NAU caused by whistler-mode signals can significantly affect heater-induced perturbations and partially explain unique results obtained at other heater sites.
BibTeX:
@article{Pradipta2008,
  author = {R Pradipta and J A Cohen and M C Lee and A Labno and L M Burton and R J Riddolls and O V Batishchev and A J Coster and W J Burke and M J Starks and M P Sulzer and S P Kuo},
  title = {Space plasma disturbances caused by NAU-launched whistler waves},
  journal = {Physica Scripta},
  year = {2008},
  volume = {T132},
  pages = {014031 (9pp)},
  url = {http://iopscience.iop.org.sci-hub.org/1402-4896/2008/T132/014031/},
  doi = {10.1088/0031-8949/2008/T132/014031}
}
Raizada S, Sulzer MP, Tepley CA, Gonzalez SA and Nicolls MJ (2008), "Inferring D region parameters using improved incoherent scatter radar techniques at Arecibo", Journal of Geophysical Research: Space Physics. Vol. 113(A12), pp. n/a-n/a.
Abstract: With the increased sensitivity and bandwidth, Arecibo 430 MHz incoherent scatter radar was run on 23 July 2006 using two radar modes with a focus on measuring D region parameters. One mode measured the ion line spectra over D region altitudes; the other mode was used as a new way to calibrate the electron densities in the D region and also to correct the ion line spectra. The ion line primarily provided a power profile connecting the D region to altitudes where the plasma line is useful. The plasma line provided the absolute electron density, used in the lower altitudes for calibration, and at F region altitudes for determining the baseline level in the D region spectra due to the folding-in of F region scattered power. It is found that the electron line contribution is about 1–3 times the ion line between 60–75 km altitude ranges. Electron concentration was found to be in the range of a few hundred to 5000 cm?3 in the 65–90 km altitude range. The new technique agrees well with the previous measurements. The D region spectral widths were used to calculate the ratio of negative ion to electron concentration (?). Between 0900 and 1100 LT, a 4 km thick layer of negative ions was observed with ? ? 1.6 ± 0.3 around 73–77 km. In the altitude range of 81–91 km, we inferred temperatures ? 195–215 K using ion-neutral collision frequencies determined from the spectral widths.
BibTeX:
@article{Raizada2008,
  author = {Raizada, Shikha and Sulzer, Michael P. and Tepley, Craig A. and Gonzalez, Sixto A. and Nicolls, Michael J.},
  title = {Inferring D region parameters using improved incoherent scatter radar techniques at Arecibo},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2008},
  volume = {113},
  number = {A12},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2007JA012882},
  doi = {10.1029/2007JA012882}
}
Roy A, Wen C-H, Doherty J and Mathews J (2008), "Signal Feature Extraction From Microbarograph Observations Using the Hilbert-Huang Transform", IEEE Transactions on Geoscience and Remote Sensing. Vol. 46(5), pp. 1442-1447.
Abstract: The Hilbert-Huang transform (HHT) is a relatively new time-frequency analysis tool. We present a new signal feature extraction technique based on HHT. This technique is used to extract diurnal and semidiurnal tides from atmospheric pressure data obtained from a microbarograph stationed at the Arecibo Observatory. Observation of seasonal variations of semidiurnal tides is possible due to the high precision offered by this technique. Furthermore, we apply the signal extraction procedure to isolate and remove high-amplitude disturbance signals from the time-series signal. This is demonstrated by extracting a hurricane event from the pressure data. The superior capabilities of the HHT-based technique to analyze time-varying signals compared to traditional linear techniques such as the wavelet transform and the fast Fourier transform are demonstrated.
BibTeX:
@article{Roy2008,
  author = {Roy, A. and Chun-Hsien Wen and Doherty, J.F. and Mathews, J.D.},
  title = {Signal Feature Extraction From Microbarograph Observations Using the Hilbert-Huang Transform},
  journal = {IEEE Transactions on Geoscience and Remote Sensing},
  year = {2008},
  volume = {46},
  number = {5},
  pages = {1442-1447},
  doi = {10.1109/TGRS.2007.909916}
}
Seker I, Livneh DJ, Makela JJ and Mathews JD (2008), "Tracking F-region plasma depletion bands using GPS-TEC, incoherent scatter radar, and all-sky imaging at Arecibo", Earth Planets Space. Vol. 60, pp. 633-646.
Abstract: F-region plasma dynamics has been one of the main foci of the ionospheric research community for decades. The mid-latitude F-region has been considered to be relatively calm; however recent observations using highly sensitive CCD imaging systems and Global Positioning System (GPS) receivers have revealed that mid-latitude F-region mesoscale electrodynamics are more complex and this region is more active than usually assumed. Here we report combined incoherent scatter radar (ISR), imager, and GPS observations of F-region Medium-Scale Traveling Ionospheric Disturbance (MSTID) structures over the Arecibo Observatory in Puerto Rico. In particular, the plasma structures seen in the narrow-beam ISR cannot be understood fully without the all-sky images, which provide the context for the radar results—specifically, the spatial and temporal properties of the mesoscale structure. The GPS-derived total electron content (TEC) data provide additional information on the intensity of the MSTIDs. Here we present analysis of two specific plasma depletion events, which we prefer to call "MSTID bands". Important results on the 3D geometry of these structures were found using a newly developed observation technique. For the first time, it is shown that the southern part of MSTID bands reaches higher altitudes than the northern part (vertically tilted by 12° towards magnetic south). These results give a much broader perspective on nighttime, mid-latitude F-region structure and point to new ways of interpreting these structures and how they appear in ISR results.
BibTeX:
@article{Seker2008,
  author = {Ilgin Seker and Dorey J. Livneh and Jonathan J. Makela and John D. Mathews},
  title = {Tracking F-region plasma depletion bands using GPS-TEC, incoherent scatter radar, and all-sky imaging at Arecibo},
  journal = {Earth Planets Space},
  year = {2008},
  volume = {60},
  pages = {633-646}
}
Vondrak T, Plane JMC, Broadley S and Janches D (2008), "A chemical model of meteoric ablation", Atmospheric Chemistry and Physics. Vol. 8(23), pp. 7015-7031.
Abstract: Most of the extraterrestrial dust entering the Earth's atmosphere ablates to produce metal vapours, which have significant effects on the aeronomy of the upper mesosphere and lower thermosphere. A new Chemical Ablation Model (CAMOD) is described which treats the physics and chemistry of ablation, by including the following processes: sputtering by inelastic collisions with air molecules before the meteoroid melts; evaporation of atoms and oxides from the molten particle; diffusion-controlled migration of the volatile constituents (Na and K) through the molten particle; and impact ionization of the ablated fragments by hyperthermal collisions with air molecules. Evaporation is based on thermodynamic equilibrium in the molten meteoroid (treated as a melt of metal oxides), and between the particle and surrounding vapour phase. The loss rate of each element is then determined assuming Langmuir evaporation. CAMOD successfully predicts the meteor head echo appearance heights, observed from incoherent scatter radars, over a wide range of meteoroid velocities. The model also confirms that differential ablation explains common-volume lidar observations of K, Ca and Ca+ in fresh meteor trails. CAMOD is then used to calculate the injection rates into the atmosphere of a variety of elements as a function of altitude, integrated over the meteoroid mass and velocity distributions. The most abundant elements (Fe, Mg and Si) have peak injection rates around 85 km, with Na and K about 8 km higher. The more refractory element Ca ablates around 82 km with a Na:Ca ratio of 4:1, which does therefore not explain the depletion of atomic Ca to Na, by more than 2 orders of magnitude, in the upper mesosphere. Diffusion of the most volatile elements (Na and K) does not appear to be rate-limiting except in the fastest meteoroids. Non-thermal sputtering causes ~35% mass loss from the fastest (~60–70 km s?1) and smallest (10?17–10?13 g) meteoroids, but makes a minor contribution to the overall ablation rate.
BibTeX:
@article{Vondrak2008,
  author = {Vondrak, T. and Plane, J. M. C. and Broadley, S. and Janches, D.},
  title = {A chemical model of meteoric ablation},
  journal = {Atmospheric Chemistry and Physics},
  year = {2008},
  volume = {8},
  number = {23},
  pages = {7015-7031},
  doi = {10.5194/acp-8-7015-2008}
}
Waldrop LS, Kerr R and Richards P (2008), "Photoelectron impact excitation of OI 8446 A emission observed from Arecibo Observatory", Journal of Geophysical Research: Space Physics. Vol. 113(A1), pp. n/a-n/a.
Abstract: Photoelectron (PE) impact on thermospheric oxygen atoms is a major source of OI 8446 Å emission excitation at midlatitudes. However, historical discrepancies between observed twilight emission brightnesses and PE model predictions have not only prompted speculation regarding secondary sources of excitation but also precluded the use of observed brightness as a much-needed diagnostic of thermospheric O density. In an effort to improve understanding of the physical mechanisms responsible for its excitation, this paper presents new photometric measurements of twilight OI 8446 Å emission brightness, together with calculations using the Field Line Interhemispheric Plasma (FLIP) PE model, acquired from Arecibo Observatory under geomagnetically quiet conditions during three winter campaigns from 1999–2002. Winter is a particularly favorable season for twilight 8446 Å observation in the northern hemisphere since significant PE production, and thus 8446 Å excitation, persists for several hours in the fully illuminated, geomagnetic conjugate hemisphere in the absence of any local thermospheric illumination. The winter 8446 Å brightness data are fully consistent with a dominant PE impact excitation source. However, the new data also confirm the Lancaster et al. (2000) report of excess early morning brightness at Arecibo with respect to PE models which use a tilted-dipole approximation to the geomagnetic field. By using the International Geomagnetic Reference Field (IGRF) geomagnetic field model to refine Arecibo's conjugate point location specified in the FLIP PE model, we demonstrate significantly improved agreement between the modeled and observed brightness decay profiles during both morning and evening twilight intervals.
BibTeX:
@article{Waldrop2008,
  author = {Waldrop, L. S. and Kerr, R. and Richards, P.},
  title = {Photoelectron impact excitation of OI 8446 A emission observed from Arecibo Observatory},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2008},
  volume = {113},
  number = {A1},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2007JA012356},
  doi = {10.1029/2007JA012356}
}
Zarka P, Farrell W, Fischer G and Konovalenko A (2008), "Ground-Based and Space-Based Radio Observations of Planetary Lightning", Space Science Reviews. Vol. 137(1-4), pp. 257-269.
Abstract: We review radio detection of planetary lightning performed by Voyager, Galileo (including in-situ probe measurements), Cassini, and other spacecraft, and compare the information on the underlying physics derived from these observations—especially the discharge duration, at Jupiter and Saturn—with our knowledge of terrestrial lightning. The controversial evidence at Venus is discussed, as well as the prospects for lightning-like discharges in Martian dust-storms (and studies on terrestrial analogues). In addition, lightning sources provide radio beacons that allow us to probe planetary ionospheres. Ground-based observations of Saturn’s lightning have been attempted several times in the past and have been recently successful. They will be the subject of observations by the new generation of giant radio arrays. We review past results and future studies, focussing on the detection challenges and on the interest of ground-based radio monitoring, in conjunction with spacecraft observations or in standalone mode.
BibTeX:
@article{Zarka2008,
  author = {Zarka, P. and Farrell, W. and Fischer, G. and Konovalenko, A.},
  title = {Ground-Based and Space-Based Radio Observations of Planetary Lightning},
  journal = {Space Science Reviews},
  year = {2008},
  volume = {137},
  number = {1-4},
  pages = {257-269},
  url = {http://dx.doi.org/10.1007/s11214-008-9366-8},
  doi = {10.1007/s11214-008-9366-8}
}
Zhou Q, Raizada S, Tepley CA and Plane JM (2008), "Seasonal and diurnal variation of electron and iron concentrations at the meteor heights above Arecibo", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 70(1), pp. 49-60.
Abstract: We report observations of seasonal and local time variation of the averaged electron and iron concentrations, as well as simultaneous measurements of the two species, above the Arecibo Observatory (18.35°N, 66.75°N), Puerto Rico. The average Fe profile between 21:00 and 24:00 LT has a single peak at about 85 km with the exception of the summer when an additional peak exists at about 95 km. The higher Fe peak in the summer is correlated with higher electron concentrations in this season. The three nights of simultaneous measurements of electron and iron concentrations show that narrow layers of Fe and electrons are well correlated. Comparison of the climatological and simultaneous Fe and electron data suggests that recombination of Fe+ plays an important role in determining the Fe profile in the upper part of the Fe layer. Above 93 km, the Fe concentration appears to increase after sunset if the electron concentration exceeds about 4000 electrons cm?3. The average rate of Fe production is about 0.1 atom cm?3 s?1 for all seasons at 100 km in the early evening hours. A chemical model reveals that the concentration of Fe+ must be 50–80% of the total ionization over Arecibo for typical equinox conditions to explain the observed rate of Fe production. These high relative Fe+ concentrations are consistent with in situ observations that Fe+ is usually the dominant ion in sporadic E layers in the nighttime lower E region. This suggests that the source of Fe+ is provided by sporadic E layers descending over Arecibo after sunset. The Fe density between 80 and 85 km decreases during the night, for all seasons. This is attributed to the formation of stable molecular Fe species, such as FeOH, due to the increase in O3 and decrease in atomic O and H during the night at these altitudes.
BibTeX:
@article{Zhou2008,
  author = {Qihou Zhou and Shikha Raizada and Craig A. Tepley and John M.C. Plane},
  title = {Seasonal and diurnal variation of electron and iron concentrations at the meteor heights above Arecibo},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2008},
  volume = {70},
  number = {1},
  pages = {49-60},
  doi = {10.1016/j.jastp.2007.09.012}
}
Fentzke JT, Friedman JS and Janches D (2008), "High resolution potassium lidar meteor trail observations at Arecibo: Preliminary results.", In 25th International Laser Radar Conference.
BibTeX:
@conference{,
  author = {J. T. Fentzke and J. S. Friedman and D. Janches},
  title = {High resolution potassium lidar meteor trail observations at Arecibo: Preliminary results.},
  booktitle = {25th International Laser Radar Conference},
  year = {2008}
}
Brum CGM and Lewis M (2008), "Research Experience for Undergraduates Program, PROGRESS REPORT SUMMER 2008"
BibTeX:
@techreport{,
  author = {Brum, Christiano Garnett Marques and Lewis, Murray},
  title = {Research Experience for Undergraduates Program, PROGRESS REPORT SUMMER 2008},
  year = {2008}
}
(2007), "Arecibo radar under pressure", Astronomy & Geophysics. Vol. 48(4), pp. 4.05. Blackwell Publishing Ltd.
Abstract: The planetary radar at Arecibo Observatory, the most powerful in the world, is short of money and may have to close.
BibTeX:
@article{AAG:AAG48404_5,,
  title = {Arecibo radar under pressure},
  journal = {Astronomy & Geophysics},
  publisher = {Blackwell Publishing Ltd},
  year = {2007},
  volume = {48},
  number = {4},
  pages = {4.05},
  url = {http://dx.doi.org/10.1111/j.1468-4004.2007.48404_5.x},
  doi = {10.1111/j.1468-4004.2007.48404_5.x}
}
Aponte N, Sulzer MP, Nicolls MJ, Nikoukar R and Gonzalez SA (2007), "Molecular ion composition measurements in the F1 region at Arecibo", Journal of Geophysical Research: Space Physics. Vol. 112(A6), pp. n/a-n/a.
Abstract: The molecular ion composition in the F1 region is extremely difficult to measure with incoherent scatter (IS) radars because of the temperature/ion composition ambiguity in the shape of the incoherent scatter ion line spectrum. In practice, this means that a nonlinear least squares fitting (LSF) analysis of IS ion line data in this region can find different combinations of ionospheric parameters to be equally good fits. The only way to mitigate this problem is to add additional information to reduce the number of unknown parameters that need to be determined by the nonlinear least squares fitting. Following the concept originally reported by Waldteufel (1971), we have implemented a technique to combine the very precise electron density information in the plasma line with very accurate ion line spectra to measure the F1 region molecular ion composition. In this study, we describe the technique and show the first results from this method.
BibTeX:
@article{Aponte2007,
  author = {Aponte, Nestor and Sulzer, Michael P. and Nicolls, Michael J. and Nikoukar, Romina and Gonzalez, Sixto A.},
  title = {Molecular ion composition measurements in the F1 region at Arecibo},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2007},
  volume = {112},
  number = {A6},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2006JA012028},
  doi = {10.1029/2006JA012028}
}
Friedman JS and Chu X (2007), "Nocturnal temperature structure in the mesopause region over the Arecibo Observatory (18.35 N, 66.75 W): Seasonal variations", Journal of Geophysical Research: Atmospheres. Vol. 112(D14), pp. n/a-n/a.
Abstract: We present the mean seasonal climatology of the nocturnal temperature structure in the mesopause region (80–105 km) above the Arecibo Observatory, Puerto Rico (18.35°N, 66.75°W) from 106 nights of potassium Doppler lidar observations between December 2003 and September 2006. This first complete range-resolved mesopause climatology for a tropical latitude exhibits several unique features. Compared to higher latitude sites, mesospheric temperature inversion layers in the nocturnal means are much weaker at Arecibo. Seasonally large inversions occur in summer but are almost non-existent during the rest of the year. The Arecibo climatology shows a three-level mesopause: a high altitude in summer (~100 km), a medium altitude in late autumn and winter (~96 km), and a low altitude in early spring (~91 km). The mesopause is cold in the solstices (~171 K in summer, ~176 K in winter) and warm around equinoxes, particularly late autumn when it is near 195 K, while the spring mesopause temperature is close to 185 K. The lower thermosphere around 100 km at Arecibo shows a decreasing temperature from spring to summer when it reaches its coldest temperature, which is contrary to the increasing temperature observed at all midlatitude locations. Semiannual variations in the seasonal temperature have amplitudes as large as the annual variations through most of the MLT altitude range at Arecibo. These observed seasonal variations appear to be associated with the semi-annual oscillation, a predominantly tropical phenomenon. This report provides one of the very few observations of the semi-annual oscillation in lower thermosphere temperature.
BibTeX:
@article{Friedman2007,
  author = {Friedman, Jonathan S. and Chu, Xinzhao},
  title = {Nocturnal temperature structure in the mesopause region over the Arecibo Observatory (18.35 N, 66.75 W): Seasonal variations},
  journal = {Journal of Geophysical Research: Atmospheres},
  year = {2007},
  volume = {112},
  number = {D14},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2006JD008220},
  doi = {10.1029/2006JD008220}
}
Goncharenko L, Foster J, Coster A, Huang C, Aponte N and Paxton L (2007), "Observations of a positive storm phase on September 10, 2005", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 69(10-11), pp. 1253-1272.
Abstract: In this study, we present multi-instrument observations of a strong positive phase of ionospheric storm, which occurred on September 10, 2005 during a moderate geomagnetic storm with minimum Dst=-60nT and maximum Kp=6-. The daytime electron density measured by the Millstone Hill incoherent scatter radar (42.6oN, 288.5oE) increased after 13UT (8LT) compared with that before the storm. This increase is observed throughout the daytime, lasts for about 9h, and covers F-region altitudes above ~230km. At the altitude of 300km, the maximum increase in Ne reaches a factor of 3 by 19:30-20:00UT and is accompanied by a ~1000K decrease in electron temperature, a ~100-150K increase in ion temperature, and a strong upward drift. Observations by Arecibo ISR (18.3oN, 293.3oE) reveal similar features, with the maximum increase in electron density reaching a factor of 2.5 at 21:30UT, i.e. 1.5-2h later than over Millstone Hill. The GPS TEC data show that the increase in electron density observed at Millstone Hill and Arecibo is only a part of a global picture reflected in TEC. The increase in TEC reaches a factor of 2 and covers middle and low latitudes at 19UT. At later times this increase moves to lower latitudes. A combination of mechanisms were involved in generation of positive phase. The penetration electric field resulted in Ne enhancements at subauroral and middle latitudes, the TAD/TID played an important role at middle and lower latitudes, and increase in O/N2 ratio could contribute to the observed positive phase at middle and lower latitudes. The results show the importance of an upward vertical drift at ~140-250km altitude, which is observed for sustained period of time and assists in the convergence of ionization into the F-region.
BibTeX:
@article{Goncharenko2007,
  author = {L.P. Goncharenko and J.C. Foster and A.J. Coster and C. Huang and N. Aponte and L.J. Paxton},
  title = {Observations of a positive storm phase on September 10, 2005},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2007},
  volume = {69},
  number = {10-11},
  pages = {1253-1272},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682607000727},
  doi = {10.1016/j.jastp.2006.09.011}
}
Rodrigues FS, Nicolls MJ, Woodman R, Hysell DL, Chau JL and González SA (2007), "Ion gyroresonance observations at Jicamarca revisited", Geophysical Research Letters. Vol. 34(13), pp. n/a-n/a.
Abstract: This paper presents recent observations of the proton gyroresonance over Jicamarca. In October 2006, a single-polarization double-pulse experiment was set up to measure the first gyroresonance peak in the incoherent scatter (IS) auto-correlation function (ACF). Despite the clutter caused by Spread-F and artificial satellites, it was possible to measure the first proton gyroresonance peak of the ACF in the topside ionosphere. For the first time, least-squares fits of theoretical IS ACFs to gyroresonance measurements are reported. Theoretical ACFs that best fit the measurements were found using the H+ fraction and temperature (assuming Te = Ti) as fitting parameters. Uncertainties for the estimated fraction of H+ were as low as 12%, while uncertainties for estimated temperatures were around 30%. These are the first successful gyroresonance measurements since the early observations of Farley (1967), and it is the first time measurements of this type have been used to obtain least squares estimates of ion composition and temperatures.
BibTeX:
@article{GRL:GRL23052,
  author = {Rodrigues, F. S. and Nicolls, M. J. and Woodman, R. and Hysell, D. L. and Chau, J. L. and González, S. A.},
  title = {Ion gyroresonance observations at Jicamarca revisited},
  journal = {Geophysical Research Letters},
  year = {2007},
  volume = {34},
  number = {13},
  pages = {n/a--n/a},
  url = {http://dx.doi.org/10.1029/2007GL029680},
  doi = {10.1029/2007GL029680}
}
Janches D and Nicolls MJ (2007), "Diurnal variability of the gyro resonance line observed with the Arecibo incoherent scatter radar at E- and F1-region altitudes", Geophysical Research Letters. Vol. 34(1), pp. n/a-n/a.
Abstract: In this paper, we report on observations of the diurnal variation of a resonance line that occurs near the gyro frequency as seen with the incoherent scatter radar (ISR) at the Arecibo Observatory. This gyro resonance line has rarely been observed in ISR data, but recent results, exemplified by the observations of Bhatt et al. (2006), have implied that the gyro line is a common ionospheric feature. The observations presented here were made with much better altitude resolution in comparison with previous results and represent full 24 hour coverage for several days. The data indicate that an increase in the gyro line intensity near sunrise and sunset is an everyday occurrence. As the increase in intensity is occurring at sunset, the gyro line frequency drops from the expected frequency to one near zero frequency. As the increase in intensity is occurring at sunrise, the gyro line frequency increases from near zero frequency to one near the expected gyro line frequency. This behavior of the gyro line frequency and intensity has not been observed before. We explain these results using normal Maxwellian incoherent scatter theory together with the diurnal variation of the density in the E and F1 regions. These results may explain previous observations of the gyro line made at Arecibo and suggest avenues of future research for studying this exciting feature of the incoherent scatter spectrum.
BibTeX:
@article{Janches2007,
  author = {Janches, Diego and Nicolls, Michael J.},
  title = {Diurnal variability of the gyro resonance line observed with the Arecibo incoherent scatter radar at E- and F1-region altitudes},
  journal = {Geophysical Research Letters},
  year = {2007},
  volume = {34},
  number = {1},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2006GL028510},
  doi = {10.1029/2006GL028510}
}
Kohenl T, Aponte N, Nicolls MJ, Robles E, Tepley CA and Gonzalez SA (2007), "A Comparison of Long-term Meridional Neutral Winds extracted from Arecibo Incoherent Scatter Radar with the Neutral Winds Obtained via Fabry Perot Interferometry", In Radar Conference, 2007 IEEE. , pp. 259-264.
Abstract: This ten-week summer study compares long term averages of the meridional (north-south) component of neutral winds obtained by Arecibo 630 nm Fabry Perot interferometry (FPI), with those obtained by the Arecibo incoherent scatter radar (ISR). Night-time meridional neutral winds from the ISR were plotted by year and by month for the period between 1985 and 2003, and compared to the plots produced by Robles et al [1], who investigated FPI derived neutral winds. The magnitude and trends of the ISR data fit well with the FPI study, indicating that the neutral wind vector rotated from southeast to due east mostly due to changes in the meridional (north-south) component. A shift in the vector over time is important for modeling the ionosphere, since neutral winds are one of three main forces in the F-region of the ionosphere (region of atmosphere starting at 150 km above the earth's surface) that drive the movement of plasma. The ionosphere is the primary medium of much RF communication, and modeling plasma movement assists in mitigating unwanted propagation effects.
BibTeX:
@conference{Kohenl2007,
  author = {Talia Kohenl and Nestor Aponte and Michael J. Nicolls and Eva Robles and Craig A. Tepley and Sixto A. Gonzalez},
  title = {A Comparison of Long-term Meridional Neutral Winds extracted from Arecibo Incoherent Scatter Radar with the Neutral Winds Obtained via Fabry Perot Interferometry},
  booktitle = {Radar Conference, 2007 IEEE},
  year = {2007},
  pages = {259-264},
  doi = {10.1109/RADAR.2007.374224}
}
Labno A, Pradipta R, Lee MC, Sulzer MP, Burton LM, Cohen JA, Kuo SP and Rokusek DL (2007), "Whistler-mode wave interactions with ionospheric plasmas over Arecibo", Journal of Geophysical Research: Space Physics. Vol. 112(A3), pp. n/a-n/a.
Abstract: The Naval transmitter, code-named NAU, in Puerto Rico emits radio waves at a power and frequency of 100 kW and 40.75 kHz, respectively. The NAU-generated 40.75 kHz whistler-mode waves are intense enough to excite lower hybrid waves and zero-frequency field-aligned ionospheric irregularities over Arecibo. It is proposed that NAU is responsible for causing the enhanced plasma lines, detected by the Arecibo 430 MHz radar in the nighttime ionosphere F region, in the presence of spread F events. The lower hybrid waves, generated in a broad range of altitudes at the wake of 40.75 kHz whistler-mode waves, have a single frequency of 40.75 kHz but with a spectrum of wavelengths. They can effectively accelerate electrons continuously along the Earth's magnetic field with energies from a fraction of 1 eV to 10 eV. These energetic streaming electrons, when detected by the Arecibo 430 MHz radar, give rise to enhanced plasma lines with a frequency spectrum of ?3.25–4.75 MHz.
BibTeX:
@article{Labno2007,
  author = {Labno, A. and Pradipta, R. and Lee, M. C. and Sulzer, M. P. and Burton, L. M. and Cohen, J. A. and Kuo, S. P. and Rokusek, D. L.},
  title = {Whistler-mode wave interactions with ionospheric plasmas over Arecibo},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2007},
  volume = {112},
  number = {A3},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2006JA012089},
  doi = {10.1029/2006JA012089}
}
Larsen MF, Hysell DL, Zhou QH, Smith SM, Friedman J and Bishop RL (2007), "Imaging coherent scatter radar, incoherent scatter radar, and optical observations of quasiperiodic structures associated with sporadic E layers", Journal of Geophysical Research: Space Physics. Vol. 112(A6), pp. n/a-n/a.
Abstract: During June and July 2002, a 30-MHz imaging coherent scatter radar was installed and operated on the island of St. Croix, to view the E region ionosphere above Arecibo, Puerto Rico. During the observing period, 10 events with discernible quasiperiodic echo structure were observed with the coherent scatter radar. In six of those events, simultaneous measurements were made with the Arecibo 430-MHz incoherent scatter radar. The imaging coherent scatter radar allows us to locate and track the echo structures within the volume illuminated by the transmitter, which shows structures that are generally aligned along wavefronts. A slight preference for motion of the structures toward the southwest is evident throughout the period, but the propagation directions and speeds vary greatly. The incoherent scatter radar measurements show a close correspondence between the occurrence of the coherent echoes and the location of the enhanced electron density structures. In particular, the coherent echoes occur when the electron density layers show uplifts.
BibTeX:
@article{Larsen2007,
  author = {Larsen, M. F. and Hysell, D. L. and Zhou, Q. H. and Smith, S. M. and Friedman, J. and Bishop, R. L.},
  title = {Imaging coherent scatter radar, incoherent scatter radar, and optical observations of quasiperiodic structures associated with sporadic E layers},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2007},
  volume = {112},
  number = {A6},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2006JA012051},
  doi = {10.1029/2006JA012051}
}
Lei J, Roble RG, Wang W, Emery BA and Zhang S-R (2007), "Electron temperature climatology at Millstone Hill and Arecibo", Journal of Geophysical Research: Space Physics. Vol. 112(A2), pp. n/a-n/a.
Abstract: In this paper, ionospheric electron temperature (Te) data for more than two solar cycles measured by the incoherent scatter radars (ISR) at Millstone Hill (42.6°N, 71.5°W) and Arecibo (18.3°N, 66.7°W) are compared with the theoretical Te calculated from the National Center for Atmospheric Research Thermosphere-Ionosphere-Electrodynamics General Circulation Model (NCAR-TIEGCM) to investigate the temporal variations of Te. The comparisons are made for both low and high solar activity conditions and for three seasons: equinox, summer, and winter. The observations show that the diurnal variation of Te is characterized by morning and evening peaks at Arecibo and by a morning peak at Millstone Hill. The occurrence and strength of the peaks at Arecibo are significantly different from those at Millstone Hill. Daytime Te tends to increase with solar activity at both stations below ?300 km. Te above 300 km generally decreases with solar activity; however, it increases with solar activity in equinox and summer at Arecibo, whereas it does so only in summer at Millstone Hill. The TIEGCM model can reproduce these variations. However, the modeled evening peak is weaker than that from observations at Arecibo. The simulations show that the daytime bulge of Te tends to occur at low latitudes and high solar activity, as seen in the observations, and the significant morning peak at low solar activity over Arecibo is associated with the equatorial anomaly. Moreover, an interesting feature predicted by the model is that the midday Te at the F2 peak height increases with solar activity when F10.7 values are less than about 100 × 10?22 W m?2 Hz?1 or larger than 190 × 10?22 W m?2 Hz?1 at Millstone Hill; so does at Arecibo when F10.7 values are larger than 100 × 10?22 W m?2 Hz?1. As a result, a positive correlation between daytime Te and Ne occurs under these conditions.
BibTeX:
@article{Lei2007,
  author = {Lei, Jiuhou and Roble, Raymond G. and Wang, Wenbin and Emery, Barbara A. and Zhang, Shun-Rong},
  title = {Electron temperature climatology at Millstone Hill and Arecibo},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2007},
  volume = {112},
  number = {A2},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2006JA012041},
  doi = {10.1029/2006JA012041}
}
Liu L, Le H, Wan W, Sulzer MP, Lei J and Zhang M-L (2007), "An analysis of the scale heights in the lower topside ionosphere based on the Arecibo incoherent scatter radar measurements", Journal of Geophysical Research: Space Physics. Vol. 112(A6), pp. n/a-n/a.
Abstract: We statistically analyze the ionospheric scale heights in the lower topside ionosphere based on the electron density (Ne) and temperature profiles observed from the incoherent scatter radar (ISR) at Arecibo (293.2°E, 18.3°N), Puerto Rico. In this study, a database containing the Arecibo ISR observations from 1966 to 2002 has been used in order to investigate the diurnal and seasonal variations and solar activity dependences of the vertical scale height (VSH), which is deduced from the electron concentration profiles defined as the value of -dh/d(ln(Ne)), and the effective scale height (Hm), which is defined as the scale height in the Chapman-alpha function to approximate the Ne profiles. As a measure of the slope of the height profiles of the topside electron density, the derived VSH and Hm show marked diurnal and seasonal variations and solar activity dependences. Their features are discussed in terms of thermal structures in the lower topside ionosphere. We also investigate the quantitative relationships between Hm, VSH, and plasma scale height (Hp) over Arecibo. The similarities and differences in these scale heights are discussed. Results suggest that both the contributions from topside temperature structure and diffusion processes can also greatly control VSH and Hm through changing the profile shape.
BibTeX:
@article{Liu2007,
  author = {Liu, Libo and Le, Huijun and Wan, Weixing and Sulzer, Mike P. and Lei, Jiuhou and Zhang, Man-Lian},
  title = {An analysis of the scale heights in the lower topside ionosphere based on the Arecibo incoherent scatter radar measurements},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2007},
  volume = {112},
  number = {A6},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2007JA012250},
  doi = {10.1029/2007JA012250}
}
Liu L, Wan W, Zhang M-L, Ning B, Zhang S-R and Holt JM (2007), "Variations of topside ionospheric scale heights over Millstone Hill during the 30-day incoherent scatter radar experiment", Annales Geophysicae. Vol. 25(9), pp. 2019-2027.
BibTeX:
@article{Liu2007a,
  author = {Liu, L. and Wan, W. and Zhang, M.-L. and Ning, B. and Zhang, S.-R. and Holt, J. M.},
  title = {Variations of topside ionospheric scale heights over Millstone Hill during the 30-day incoherent scatter radar experiment},
  journal = {Annales Geophysicae},
  year = {2007},
  volume = {25},
  number = {9},
  pages = {2019-2027},
  doi = {10.5194/angeo-25-2019-2007}
}
Liu L, Wan W, Yue X, Zhao B, Ning B and Zhang M-L (2007), "The dependence of plasma density in the topside ionosphere on the solar activity level", Annales Geophysicae. Vol. 25(6), pp. 1337-1343.
BibTeX:
@article{Liu2007b,
  author = {Liu, L. and Wan, W. and Yue, X. and Zhao, B. and Ning, B. and Zhang, M.-L.},
  title = {The dependence of plasma density in the topside ionosphere on the solar activity level},
  journal = {Annales Geophysicae},
  year = {2007},
  volume = {25},
  number = {6},
  pages = {1337-1343},
  doi = {10.5194/angeo-25-1337-2007}
}
Livneh DJ, Seker I, Djuth FT and Mathews JD (2007), "Continuous quasiperiodic thermospheric waves over Arecibo", Journal of Geophysical Research: Space Physics. Vol. 112(A7), pp. n/a-n/a.
Abstract: Incoherent scatter radar (ISR) power profile observations at Arecibo Observatory (AO) have revealed long vertical wavelength (>100 km) quasi-coherent waves with periods of ?1 hour that are observed to be nearly continuously present over two ?35-hour geomagnetically quiet observation periods. When properly filtered, results from both 22–23 March 2004 and 5–6 June 2005 provide unambiguous views of these waves. The waves are strong throughout the F region, often spanning 160 to above 500 km in altitude and are present day and night in the F2 layer. Filtering techniques that were used to better reveal the waves are extensively discussed. Barometric pressure and imager data, both of which were taken on site at Arecibo, are used to provide further insight into the nature of these waves. These waves may be linked to high-latitude medium-scale traveling ionospheric disturbances (MSTIDs) observed with the superDARN radar network and associated with E region auroral electrojet source(s) that are quasi-coherent under geomagnetic quiet conditions. As auroral-zone MSTIDs are believed to dissipate before reaching Arecibo latitudes (Vadas, 2007), various alternative sources including weather patterns are explored.
BibTeX:
@article{Livneh2007,
  author = {Livneh, D. J. and Seker, I. and Djuth, F. T. and Mathews, J. D.},
  title = {Continuous quasiperiodic thermospheric waves over Arecibo},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2007},
  volume = {112},
  number = {A7},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2006JA012225},
  doi = {10.1029/2006JA012225}
}
Martinis C and Mendillo M (2007), "Equatorial spread F-related airglow depletions at Arecibo and conjugate observations", Journal of Geophysical Research: Space Physics. Vol. 112(A10), pp. n/a-n/a.
Abstract: We present evidence of the incursion into the Caribbean region of airglow depletions associated with the equatorial Rayleigh-Taylor instability. Data from the Boston University all-sky imager located at Arecibo, Puerto Rico (18.3°N, 66.7°W, 28°N magnetic latitude), have been used to identify several nights with 630.0 nm airglow patterns that are typical signatures of equatorial spread F and distinctly different from the more common “airglow bands” frequently observed there. Two case studies (2 November 2002 and 26 February 2003) show the occurrence of simultaneous airglow depletions observed with another all-sky imager located at El Leoncito, Argentina (31.8°S, 69.3°W, 18°S magnetic latitude), relatively close to the Arecibo conjugate point. Supporting information is obtained from Defense Meteorological Satellite Program, ROCSAT-1, and GPS data, all of them showing the presence of strong ionospheric irregularities collocated with the airglow depletions. Mapping the circular field of view from Arecibo into the Southern Hemisphere reveals a distorted pattern due to the differences in the magnetic field characteristics in both hemispheres. This adds an interesting spatial complexity to the formulation of conjugate point observing programs in the Latin American longitude sector.
BibTeX:
@article{Martinis2007,
  author = {Martinis, C. and Mendillo, M.},
  title = {Equatorial spread F-related airglow depletions at Arecibo and conjugate observations},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2007},
  volume = {112},
  number = {A10},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2007JA012403},
  doi = {10.1029/2007JA012403}
}
Pradipta R, Labno A, Lee MC, Burke WJ, Sulzer MP, Cohen JA, Burton LM, Kuo SP and Rokusek DL (2007), "Electron precipitation from the inner radiation belt above Arecibo", Geophysical Research Letters. Vol. 34(8), pp. n/a-n/a.
Abstract: We examine possible correlations between occurrences of nighttime E-region plasma line (PL) enhancements over Arecibo and 40.75 kHz NAU emissions. On the night of January 1–2, 2006, the experiments were conducted from 22:00 to 6:00 local time (LT). NAU transmitter was initially turned off until 01:45 LT, when continuous operations resumed for the remainder of the experiments. Enhanced PL events lasting <10 s had central frequencies and bandwidths of about 2.5 and 1.5 MHz, respectively, indicating that Arecibo radar detected 2.3 to 8.5 eV suprathermal electrons streaming along geomagnetic fields. The rate of PL event detections increased by a factor of 2.8 after NAU turn-on. We suggest that 40.75 kHz radiation sporadically leaked though local ionosphere, probably abetted by field-aligned irregularities. The radiation propagated in whistler mode into the L = 1.35 inner radiation belt where gyroresonant interactions with trapped 390 keV electrons increased the precipitation rate.
BibTeX:
@article{Pradipta2007,
  author = {Pradipta, R. and Labno, A. and Lee, M. C. and Burke, W. J. and Sulzer, M. P. and Cohen, J. A. and Burton, L. M. and Kuo, S. P. and Rokusek, D. L.},
  title = {Electron precipitation from the inner radiation belt above Arecibo},
  journal = {Geophysical Research Letters},
  year = {2007},
  volume = {34},
  number = {8},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2007GL029807},
  doi = {10.1029/2007GL029807}
}
Raizada S, Rapp M, Lubken F-J, Hoffner J, Zecha M and Plane JMC (2007), "Effect of ice particles on the mesospheric potassium layer at Spitsbergen (78 N)", Journal of Geophysical Research: Atmospheres. Vol. 112(D8), pp. n/a-n/a.
Abstract: This paper quantitatively evaluates the influence of ice particles on the K layer by using radar and lidar measurements. The methodology involves determination of the volumetric surface area [Aice] of the ice particles in a noctilucent cloud by combining a microphysical ice particle model with a charging model to produce an empirical proxy for polar mesosphere summer echoes (PMSE) based on the properties of the charged aerosol particles. The altitudinal variation of [Aice] reveals peak values of about 2.2 × 10-8 cm-1 around 85 km. The first-order loss rate of atomic K due to uptake on the ice particles maximizes close to 2.2 × 10-4 s-1 at 85 km. To examine the variability of [Aice] on background parameters, a sensitivity study showed that a ±10% variation in [Aice] can result from either a ±5 K shift in the temperatures relative to a background profile or from a ±30% change in the water vapor concentration. We found that the peak [Aice] remains constant for a change of +4 to –6 K temperature fluctuations over the altitude range of 83–85 km. Finally, a new atmospheric model of potassium predicts profiles of the K layer in early May and July that are in good agreement with the observations, when the seasonally averaged K ablation flux at 79°N is set to 160 atom cm-2 s-1. This study reveals that both the vertical wind and ice particles play a significant role in controlling the K layer distribution at high latitudes.
BibTeX:
@article{Raizada2007,
  author = {Raizada, Shikha and Rapp, Markus and Lubken, F.-J. and Hoffner, J. and Zecha, M. and Plane, J. M. C.},
  title = {Effect of ice particles on the mesospheric potassium layer at Spitsbergen (78 N)},
  journal = {Journal of Geophysical Research: Atmospheres},
  year = {2007},
  volume = {112},
  number = {D8},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2005JD006938},
  doi = {10.1029/2005JD006938}
}
Seker I, Mathews JD, Wiig J, Gutierrez PF, Friedman JS and Tepley CA (2007), "First results from the Penn State Allsky Imager at the Arecibo Observatory", Earth Planets Space. Vol. 59, pp. 165-176.
Abstract: The Penn State Allsky imager (PSASI), a user-owned-public-access (UOPA) instrument installed at Arecibo Observatory (AO: 18.3°N, 66.75°W; altitude: 350 m a.s.l.; L = 1.43 at 300 km; dip angle: 46°; geomagnetic coordinates: 29°N, 5.5°E), is a CCD-based high-resolution allsky optical imager that has been collecting ionospheric airglow data at night since May 2003. The computer controlled six-position filter wheel is equipped with three filters at 630 nm (red), 557.7 nm (green), and 777.4 nm (near-IR), respectively, which correspond to ionosphere-related oxygen emissions. The imager data, taken for more than 3.5 years now, is being used to study various ionospheric processes, such as mapped equatorial spread-F plumes, E-region gravity waves, among other, in conjunction with the AO incoherent scatter radar (ISR), mesosphere and lower thermosphere (MLT) metals lidar, and other instruments, including microbarographs. Data availability and quality as well as specific airglow events on both small/large time/spatial scales are examined, categorized, and made freely available at a data-server website. Our goal here is to briefly review the airglow science enabled by allsky imaging at AO, to describe the instrument and the data-collection methodology, and to present some of the significant results, including airglow events that correspond to ISR results.
BibTeX:
@article{Seker2007,
  author = {Ilgin Seker and John D. Mathews and Johannes Wiig and Paloma F. Gutierrez and Jonathan S. Friedman and Craig A. Tepley},
  title = {First results from the Penn State Allsky Imager at the Arecibo Observatory},
  journal = {Earth Planets Space},
  year = {2007},
  volume = {59},
  pages = {165-176},
  url = {http://adsabs.harvard.edu/abs/2007EP%26S...59..165S}
}
Strelnikova I, Rapp M, Raizada S and Sulzer M (2007), "Meteor smoke particle properties derived from Arecibo incoherent scatter radar observations", Geophysical Research Letters. Vol. 34(15), pp. n/a-n/a.
Abstract: We present a new algorithm to infer information on the properties of charged meteoric smoke particles (MSPs) from the shape of incoherent scatter radar spectra. We show that in the presence of charged MSPs the spectrum can be approximated as the sum of two Lorentzians. These two distinct spectral lines correspond to two diffusion modes in the D-region plasma, i.e., one due the presence of positive ions and one because of heavy charged MSPs. The widths and amplitudes of these two spectral lines yield information on the radius and number density (the latter only for positively charged particles) of the charged MSPs. We apply this new algorithm to measurements obtained with the 430 MHz ISR at Arecibo and demonstrate that the observed spectra indeed bear the features anticipated in the presence of charged MSPs. Resulting values of retrieved MSP number densities and radii fall well within the range of values expected from models and independent in situ observations.
BibTeX:
@article{Strelnikova2007,
  author = {Strelnikova, Irina and Rapp, Markus and Raizada, Shikha and Sulzer, Mike},
  title = {Meteor smoke particle properties derived from Arecibo incoherent scatter radar observations},
  journal = {Geophysical Research Letters},
  year = {2007},
  volume = {34},
  number = {15},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2007GL030635},
  doi = {10.1029/2007GL030635}
}
Wen C-H, Briczinski S, Livneh D, Doherty J and Mathews J (2007), "Pulse-level interference and meteor processing of Arecibo ISR data", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 69(9), pp. 973-980.
BibTeX:
@article{Wen2007,
  author = {C.-H. Wen and S.J. Briczinski and D.J. Livneh and J.F. Doherty and J.D. Mathews},
  title = {Pulse-level interference and meteor processing of Arecibo ISR data},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2007},
  volume = {69},
  number = {9},
  pages = {973-980},
  doi = {10.1016/j.jastp.2007.03.004}
}
Zhang S-R, Holt JM, Bilitza DK, van Eyken T, McCready M, Amory-Mazaudier C, Fukao S and Sulzer M (2007), "Multiple-site comparisons between models of incoherent scatter radar and IRI", Advances in Space Research . Vol. 39(5), pp. 910-917.
Abstract: Long-term databases of multiple incoherent scatter radars (ISRs) are used to create local empirical models at seven ISR sites including, from magnetic north to south and east to west, EISCAT Svalbard Radar (Norway), Sondrestrom Radar (Greenland), EISCAT TromsøRadars (Norway), Millstone Hill Radar (USA), St. Santin Radar (France), Shigaraki Middle and Upper atmosphere (MU) Radar (Japan) and Arecibo Radar (Puerto Rico). As local models, they can represent some features that may be smeared out in a global model, and are important complements to and validation tools for global models such as IRI. This paper presents comparisons between these ISR models and IRI for median solar activity and quiet magnetic activity conditions, with focus on daytime height variations for electron density, ion and electron temperatures.
BibTeX:
@article{Zhang2007,
  author = {Shun-Rong Zhang and John M. Holt and Dieter K. Bilitza and Tony van Eyken and Mary McCready and Christine Amory-Mazaudier and Shoichiro Fukao and Michael Sulzer},
  title = {Multiple-site comparisons between models of incoherent scatter radar and IRI},
  journal = {Advances in Space Research },
  year = {2007},
  volume = {39},
  number = {5},
  pages = {910-917},
  url = {http://www.sciencedirect.com/science/article/pii/S0273117706004364},
  doi = {10.1016/j.asr.2006.05.027}
}
Freire P (2007), "Research Experience for Undergraduates Program, PROGRESS REPORT SUMMER 2007"
BibTeX:
@techreport{,
  author = {Paulo Freire},
  title = {Research Experience for Undergraduates Program, PROGRESS REPORT SUMMER 2007},
  year = {2007}
}
Abdu M, Ramkumar T, Batista I, Brum C, Takahashi H, Reinisch B and Sobral J (2006), "Planetary wave signatures in the equatorial atmosphere-ionosphere system, and mesosphere- E- and F-region coupling", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 68(3-5), pp. 509-522.
Abstract: Upward transport of wave energy and momentum due to gravity, tidal and planetary waves from below and extra-tropics controls the phenomenology of the equatorial atmosphere–ionosphere system. An important aspect of this phenomenology is the development of small- and large-scale structures including thin layers in the mesosphere and E-region, and the formation of wide spectrum plasma structures of the equatorial F-region, widely known as equatorial spread F/plasma bubble irregularities (that are known to have significant impact on space application systems based on trans-ionospheric radio waves propagation). It seems that the effects of tidal and gravity waves at mesospheric and thermospheric heights and their control of ionospheric densities, electric fields and currents are relatively better known than are the effects originating from vertical coupling due to planetary waves. Results from airglow, radar and ionospheric sounding observations demonstrate the existence of significant planetary wave influence on plasma parameters at E- and F-region heights over equatorial latitudes. We present and discuss here some results showing planetary wave oscillations in concurrent mesospheric winds and equatorial electrojet intensity variations in the Indian sector as well as in the mesospheric airglow and F-layer height variation in Brazil. Also presented are evidences of planetary wave-scale oscillations in equatorial evening pre-reversal electric field (F-region vertical drift) and their effects on equatorial spread F /plasma bubble irregularity development and day-to-day variability.
BibTeX:
@article{Abdu2006,
  author = {M.A. Abdu and T.K. Ramkumar and I.S. Batista and C.G.M. Brum and H. Takahashi and B.W. Reinisch and J.H.A. Sobral},
  title = {Planetary wave signatures in the equatorial atmosphere-ionosphere system, and mesosphere- E- and F-region coupling},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2006},
  volume = {68},
  number = {3-5},
  pages = {509-522},
  note = {Vertical Coupling in the Atmosphere/Ionosphere System 2nd IAGA/ICMA Workshop on Vertical Coupling in the Atmosphere/Ionosphere System, Bath, UK, 12 - 15 July, 2004 },
  url = {http://www.sciencedirect.com/science/article/pii/S1364682605002592},
  doi = {10.1016/j.jastp.2005.03.019}
}
Abdu MA, Batista PP, Batista IS, Brum CGM, Carrasco AJ and Reinisch BW (2006), "Planetary wave oscillations in mesospheric winds, equatorial evening prereversal electric field and spread F", Geophysical Research Letters. Vol. 33(7), pp. L07107 (4 pages).
Abstract: Analysis of the MLT region winds measured by a meteor radar and the evening F region vertical plasma drift (prereversal zonal electric field -PRE) measured by digisondes over low latitude sites in Brazil, provide evidence of planetary wave (PW) scale oscillations of episodic nature simultaneously at mesospheric and F region heights. 4-day and 7-day periods are found to dominate the event analyzed. The PW scale oscillations in the PRE produces strong modulation in the equatorial spread F (ESF) irregularity processes as diagnosed by the digisondes. Considerations on the PRE development mechanism involving the E layer integrated conductivity including the effect of metallic ions and tidal winds point to the source of the PRE oscillations to be PW modulation of E region tidal winds. The PW oscillations in PRE appear to be an important source of the day-to-day variability in the ESF.
BibTeX:
@article{Abdu2006a,
  author = {Abdu, M. A. and Batista, P. P. and Batista, I. S. and Brum, C. G. M. and Carrasco, A. J. and Reinisch, B. W.},
  title = {Planetary wave oscillations in mesospheric winds, equatorial evening prereversal electric field and spread F},
  journal = {Geophysical Research Letters},
  year = {2006},
  volume = {33},
  number = {7},
  pages = {L07107 (4 pages)},
  url = {http://dx.doi.org/10.1029/2005GL024837},
  doi = {10.1029/2005GL024837}
}
Bhatt AN, Gerken Kendall EA, Kelley MC, Sulzer MP and Shume EB (2006), "Observations of strong gyro line spectra at Arecibo near dawn", Geophysical Research Letters. Vol. 33(14), pp. n/a-n/a.
Abstract: Experiments performed near dawn during the PARS Summer School at Arecibo in August 2004 show clear evidence of the gyro line in the incoherent scatter radar (ISR) spectra with only six minutes of signal integration. A very weak gyro line was first observed by Behnke and Hagen (1978) requiring two hours of signal integration. Electrons that resonate with the gyro wave mode are well within the thermal distribution. At this point we know of no theory to explain the magnitude of the gyro lines we have detected although it seems clear that the presence of photoelectrons is related to it. We present the experimental results and a comparison with an incoherent scatter numerical model based on the theory developed by Trulsen and Bjørn (1978), which shows a very good correlation. From this comparison, and by combining the gyro line and the plasma line techniques, it is possible to make electron temperature measurements.
BibTeX:
@article{Bhatt2006,
  author = {Bhatt, A. N. and Gerken Kendall, E. A. and Kelley, M. C. and Sulzer, M. P. and Shume, E. B.},
  title = {Observations of strong gyro line spectra at Arecibo near dawn},
  journal = {Geophysical Research Letters},
  year = {2006},
  volume = {33},
  number = {14},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2006GL026139},
  doi = {10.1029/2006GL026139}
}
Bishop RL, Aponte N, Earle GD, Sulzer M, Larsen MF and Peng GS (2006), "Arecibo observations of ionospheric perturbations associated with the passage of Tropical Storm Odette", Journal of Geophysical Research: Space Physics. Vol. 111(A11), pp. A11320 (9 pages).
Abstract: A suite of instruments including incoherent scatter radar, ionosonde, and a satellite-bourne GPS receiver observed the ionosphere immediately following the passage of a tropical storm. Tropical Storm Odette formed on 4 December 2003 and proceeded northeasterly over the next 4 days, passing within 600 km of the Arecibo Observatory (AO). On the night of 7–8 December AO measured F region plasma densities and velocities nearly coincident with the storm. Large velocity variations, 10–80 m/s, are evident in the plasma drift components. The variations appear wave-like with an average period of 90 min at 367 km. Zonal drifts were observed with magnitudes significantly greater than commonly observed for similar geomagnetic conditions. The Ramey ionosonde observed intense midlatitude spread F on the night following the closest passage of the storm. GPS occultations within the storm path showed an increase in gravity wave activity and F region scintillation. Combining the local increase in gravity wave activity with the large drift variations and dominant meridional electric field observed immediately following the storm's traversal of the flux tube coincident with the AO observing volume provide insight into coupling between mesoscale weather systems and the ionosphere.
BibTeX:
@article{Bishop2006,
  author = {Bishop, R. L. and Aponte, N. and Earle, G. D. and Sulzer, M. and Larsen, M. F. and Peng, G. S.},
  title = {Arecibo observations of ionospheric perturbations associated with the passage of Tropical Storm Odette},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2006},
  volume = {111},
  number = {A11},
  pages = {A11320 (9 pages)},
  url = {http://dx.doi.org/10.1029/2006JA011668},
  doi = {10.1029/2006JA011668}
}
Brum C, Abdu M, Batista I, Carrasco A and Terra P (2006), "Numerical simulation of nighttime electron precipitation in the lower ionosphere over a sub-auroral region ", Advances in Space Research . Vol. 37(5), pp. 1051-1057.
Abstract: This work presents computational simulations of electron precipitation events in the lower ionosphere to explain 30MHz riometer absorption events registered at the Brazilian Antarctic Station - BAS (62.56S; 58.39W). The simulations are based on the calculation of ion production rates from different sources (interplanetary and geocoronal ultraviolet radiations, energetic electrons and cosmic rays) and the use of a detailed ion chemical scheme to obtain the electron density which is then used to calculate the absorption at 30MHz. The electron density calculations were performed using the continuity equations for 25 positive ions and 10 negative ions, involving 175 chemical reactions, that are solved under chemical equilibrium condition. The simulation results show that a flux of about 2.5x1e6 electrons/cm-2/s-1 can increase the ionospheric cosmic noise absorption by 1 dB. The results also show that the amplitude of the maximum absorption is sensitive to variations in the precipitated electron flux in the energy range of 98-320 keV that affect most the height region of 65-85km, and that a larger contribution of the ionospheric absorption due to electron precipitation arising from above the height of absorption peak (rather than from below it), that is, the lower energy range of the precipitated electron spectra has a more dominant contribution to the attenuation of the galactic cosmic noise signal.
BibTeX:
@article{Brum2006,
  author = {C.G.M. Brum and M.A. Abdu and I.S. Batista and A.J. Carrasco and P.M. Terra},
  title = {Numerical simulation of nighttime electron precipitation in the lower ionosphere over a sub-auroral region },
  journal = {Advances in Space Research },
  year = {2006},
  volume = {37},
  number = {5},
  pages = {1051-1057},
  url = {http://www.sciencedirect.com/science/article/pii/S0273117706000342},
  doi = {10.1016/j.asr.2006.02.003}
}
Cerruti AP, Kintner PM, Gary DE, Lanzerotti LJ, de Paula ER and Vo HB (2006), "Observed solar radio burst effects on GPS/Wide Area Augmentation System carrier-to-noise ratio", Space Weather. Vol. 4(10), pp. n/a-n/a.
Abstract: The first direct observations of Global Positioning System (GPS) L1 (1.57542 GHz) carrier-to-noise ratio degradation due to a solar radio burst are presented for an event that occurred on 7 September 2005. Concurrent carrier-to-noise ratio data from GPS satellites are available from receivers at Arecibo Observatory, Puerto Rico; San Juan, Puerto Rico; and also from Anderson, South Carolina, United States. The right-hand circularly polarized (RHCP) signals from this solar radio burst caused a corresponding decrease in the carrier-to-noise ratio of about 2.3 dB across all visible satellites. The maximum solar radio burst power associated with this event was 8700 solar flux units (1 SFU = 10-22 W/m2/Hz) RHCP at 1600 MHz. Direct observations of GPS semicodeless L2 carrier-to-noise ratio degradation from receivers in Brazil are also presented for a solar radio burst that occurred on 28 October 2003. The maximum degradation at GPS L1 was about 3.0 dB, and a degradation of 10.0 dB was observed on the semicodeless L2 signal. Scaling to historic solar radio burst records suggests that GPS L1 receivers could fail to produce a navigation solution and that semicodeless L1/L2 receivers will fail.
BibTeX:
@article{Cerruti2006,
  author = {Cerruti, Alessandro P. and Kintner, Paul M. and Gary, Dale E. and Lanzerotti, Louis J. and de Paula, Eurico R. and Vo, Hien B.},
  title = {Observed solar radio burst effects on GPS/Wide Area Augmentation System carrier-to-noise ratio},
  journal = {Space Weather},
  year = {2006},
  volume = {4},
  number = {10},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2006SW000254},
  doi = {10.1029/2006SW000254}
}
Comarazamy DE, Gonzalez JE, Tepley CA, Raizada S and Pandya RVR (2006), "Effects of atmospheric particle concentration on cloud microphysics over Arecibo", Journal of Geophysical Research: Atmospheres. Vol. 111(D9), pp. n/a-n/a.
Abstract: A new cloud microphysics module incorporated to a regional atmospheric model and atmospheric particle (AP) observations performed at the Arecibo Observatory were used to simulate two short precipitation events observed in the area of the observatory and to investigate the possible effects of AP on cloud formation and rain development. First, model runs were performed with and without the new cloud module, initialized with the new AP data set and the previous cloud spectrum available. The combination of the new cloud module and the Arecibo observations produced the most satisfactory results and significant improvements in total precipitation modeled: 70 versus 80 mm observed. The improvement results in 15% more precipitation predicted when compared with the old cloud information and more than 50% with respect to simulations without cloud condensation nuclei activation. Then, a set of idealized runs showed that cloud droplet production is significantly larger in polluted air than in clear skies and that rainwater in polluted air is less than that in unpolluted air. This may be because existing droplets will compete more vigorously for the available water vapor and will not reach the necessary radius to fall, and therefore growth by collision and coalescence is subdued.
BibTeX:
@article{Comarazamy2006,
  author = {Comarazamy, Daniel E. and Gonzalez, Jorge E. and Tepley, Craig A. and Raizada, Shikha and Pandya, R. V. R.},
  title = {Effects of atmospheric particle concentration on cloud microphysics over Arecibo},
  journal = {Journal of Geophysical Research: Atmospheres},
  year = {2006},
  volume = {111},
  number = {D9},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2005JD006243},
  doi = {10.1029/2005JD006243}
}
Delgado R, Weiner BR and Friedman JS (2006), "Chemical model for mid-summer lidar observations of mesospheric potassium over the Arecibo Observatory", Geophysical Research Letters. Vol. 33(2), pp. n/a-n/a.
Abstract: To understand the mid-summer nocturnal mesospheric K layer over the Arecibo Observatory (18.35°N, 66.75°W) a one dimensional model has been developed. Focusing on nights with no sporadic layer activity, we identify possible molecular reservoirs and sinks in the K layer using ab initio calculations to estimate the thermochemistry. Reactions KN2+ + O, KN2+ + CO2, and KHCO3 + H play primary roles in the chemistry of ionic and neutral potassium in the mesospheric cycle. The predominant potassium species is KHCO3 as a result of the influence of odd oxygen/hydrogen chemistry. The study of the metal layer contributes to a better understanding of chemical and dynamic changes that affect atmospheric composition.
BibTeX:
@article{Delgado2006,
  author = {Delgado, Rubén and Weiner, Brad R. and Friedman, Jonathan S.},
  title = {Chemical model for mid-summer lidar observations of mesospheric potassium over the Arecibo Observatory},
  journal = {Geophysical Research Letters},
  year = {2006},
  volume = {33},
  number = {2},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2005GL024326},
  doi = {10.1029/2005GL024326}
}
Emmert JT, Faivre ML, Hernandez G, Jarvis MJ, Meriwether JW, Niciejewski RJ, Sipler DP and Tepley CA (2006), "Climatologies of nighttime upper thermospheric winds measured by ground-based Fabry-Perot interferometers during geomagnetically quiet conditions: 1. Local time, latitudinal, seasonal, and solar cycle dependence", Journal of Geophysical Research: Space Physics. Vol. 111(A12), pp. n/a-n/a.
Abstract: We analyze ground-based Fabry-Perot interferometer observations of upper thermospheric (~250 km) horizontal neutral winds derived from Doppler shifts in the 630.0 nm (red line) nightglow. The winds were measured over the following locations: South Pole (90°S), Halley (76°S, 27°W), Arequipa (17°S, 72°W), Arecibo (18°N, 67°W), Millstone Hill (43°N, 72°W), Sondre Strømfjord (67°N, 51°W), and Thule (77°N, 68°W). We derive climatological quiet time (Kp < 3) wind patterns as a function of local time, solar cycle, day of year, and the interplanetary magnetic field (IMF), and provide parameterized representations of these patterns. At the high-latitude stations, and at Arequipa near the geomagnetic equator, wind speeds tend to increase with increasing solar extreme ultraviolet (EUV) irradiance. Over Millstone Hill and Arecibo, solar EUV has a negative effect on wind magnitudes. As represented by the 10.7 cm radio flux proxy, the solar EUV dependence of the winds at all latitudes is characterized by a saturation or weakening of the effect above moderate values (F10.7 > 150). The seasonal dependence of the winds is generally annual, but there are isolated cases in which a semiannual variation is observed. Within the austral winter, winds measured from the South Pole show a substantial intraseasonal variation only along longitudes directed toward the magnetic pole. IMF effects are described in a companion paper.
BibTeX:
@article{Emmert2006,
  author = {Emmert, J. T. and Faivre, M. L. and Hernandez, G. and Jarvis, M. J. and Meriwether, J. W. and Niciejewski, R. J. and Sipler, D. P. and Tepley, C. A.},
  title = {Climatologies of nighttime upper thermospheric winds measured by ground-based Fabry-Perot interferometers during geomagnetically quiet conditions: 1. Local time, latitudinal, seasonal, and solar cycle dependence},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2006},
  volume = {111},
  number = {A12},
  pages = {n/a-n/a},
  doi = {10.1029/2006JA011948}
}
Fritts DC, Janches D, Riggin DM, Stockwell RG, Sulzer MP and Gonzalez S (2006), "Gravity waves and momentum fluxes in the mesosphere and lower thermosphere using 430 MHz dual-beam measurements at Arecibo: 2. Frequency spectra, momentum fluxes, and variability", Journal of Geophysical Research: Atmospheres. Vol. 111(D18), pp. n/a-n/a.
Abstract: Janches et al. (2006) described a new dual-beam use of the 430 MHz incoherent scatter radar at the Arecibo Observatory in Puerto Rico. We found the technique to define the radial wind field in the mesosphere and lower thermosphere with sufficient accuracy to characterize gravity waves occurring at high frequencies and small spatial scales over an extended altitude range. The coplanar, dual-beam experiment was also designed to test the ability of the system to measure gravity wave momentum fluxes and their frequency distributions, and we report here on those results. Initial measurements were of limited duration and necessarily represent a case study, but they demonstrate the value of such measurements for studies of GW variability and large-scale interactions. Radial velocity variances reveal preferential eastward propagation for most intervals and altitudes, with the greatest propagation bias at lower altitudes and later times on 11 September when strong westward mean winds favor strong gravity filtering. The momentum fluxes observed during this experiment had ~50-min averages that were often near zero, occasionally achieved amplitudes of ~20 to 50 m2s-2, displayed significant consistency in altitude, and exhibited an approximate anticorrelation with the zonal wind field in cases with significant momentum fluxes. Frequency spectra defined the major contributions to the momentum fluxes, while S transforms were employed to examine the temporal variability of the GWs and momentum fluxes in greater detail.
BibTeX:
@article{Fritts2006,
  author = {Fritts, David C. and Janches, Diego and Riggin, Dennis M. and Stockwell, Robert G. and Sulzer, Michael P. and Gonzalez, Sixto},
  title = {Gravity waves and momentum fluxes in the mesosphere and lower thermosphere using 430 MHz dual-beam measurements at Arecibo: 2. Frequency spectra, momentum fluxes, and variability},
  journal = {Journal of Geophysical Research: Atmospheres},
  year = {2006},
  volume = {111},
  number = {D18},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2005JD006883},
  doi = {10.1029/2005JD006883}
}
Janches D, Heinselman CJ, Chau JL, Chandran A and Woodman R (2006), "Modeling the global micrometeor input function in the upper atmosphere observed by high power and large aperture radars", Journal of Geophysical Research: Space Physics. Vol. 111(A7), pp. n/a-n/a.
BibTeX:
@article{Janches2006,
  author = {Janches, Diego and Heinselman, Craig J. and Chau, Jorge L. and Chandran, Amal and Woodman, Ronald},
  title = {Modeling the global micrometeor input function in the upper atmosphere observed by high power and large aperture radars},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2006},
  volume = {111},
  number = {A7},
  pages = {n/a-n/a},
  doi = {10.1029/2006JA011628}
}
Janches D, Fritts DC, Riggin DM, Sulzer MP and Gonzalez S (2006), "Gravity waves and momentum fluxes in the mesosphere and lower thermosphere using 430 MHz dual-beam measurements at Arecibo: 1. Measurements, methods, and gravity waves", Journal of Geophysical Research: Atmospheres. Vol. 111(D18), pp. n/a-n/a.
Abstract: We report here and in a companion paper by Fritts et al. (2006a) on a new use of the UHF radar at the Arecibo Observatory in Puerto Rico. We have employed the 430 MHz radar for incoherent scatter measurements of radial wind spectra at altitudes from ~71 to 95 km using the Gregorian and line-feed antennas to define beam angles inclined 15° to the east and west of zenith. We find that the two beams define radial velocities with sufficient accuracy to characterize both the gravity waves and the momentum fluxes due to these waves over the majority of the observed altitude range during daylight hours. The characteristics of the gravity waves inferred from these measurements include (1) vertical scales ranging from ~2 to 20 km, (2) downward phase progression of the dominant gravity waves up to ~5 ms-1, and (3) vertical wave number spectra having slopes near a value (-3) expected for saturated gravity waves. Gravity wave frequency spectra and momentum fluxes are addressed in the companion paper.
BibTeX:
@article{Janches2006a,
  author = {Janches, Diego and Fritts, David C. and Riggin, Dennis M. and Sulzer, Michael P. and Gonzalez, Sixto},
  title = {Gravity waves and momentum fluxes in the mesosphere and lower thermosphere using 430 MHz dual-beam measurements at Arecibo: 1. Measurements, methods, and gravity waves},
  journal = {Journal of Geophysical Research: Atmospheres},
  year = {2006},
  volume = {111},
  number = {D18},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2005JD006882},
  doi = {10.1029/2005JD006882}
}
Coles WA, Harmon JK, Sulzer MP, Chau JL and Woodman RF (2006), "An upper bound on the solar radar cross section at 50 MHz", Journal of Geophysical Research: Space Physics. Vol. 111(A4), pp. n/a-n/a.
Abstract: We have made 16 unsuccessful attempts, in February and October 2003, and February 2004, to observe solar echoes using the 50 MHz radar at Jicamarca in Peru. The upper bound that we have determined on the solar cross section is significantly lower than the average of earlier reported observations. In this paper we will describe the observations, discuss the noise and interference from solar bursts, and suggest possible reasons why the echo might be weaker than expected.
BibTeX:
@article{JGRA:JGRA18173,
  author = {Coles, W. A. and Harmon, J. K. and Sulzer, M. P. and Chau, J. L. and Woodman, R. F.},
  title = {An upper bound on the solar radar cross section at 50 MHz},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2006},
  volume = {111},
  number = {A4},
  pages = {n/a--n/a},
  url = {http://dx.doi.org/10.1029/2005JA011416},
  doi = {10.1029/2005JA011416}
}
Pintér B, Thom SD, Balthazor R, Vo H and Bailey GJ (2006), "Modeling subauroral polarization streams equatorward of the plasmapause footprints", Journal of Geophysical Research: Space Physics. Vol. 111(A10), pp. n/a-n/a.
Abstract: We report on a modeling study on the effects of subauroral polarization stream (SAPS) events equatorward of the plasmapause footprints, using the Sheffield Coupled Thermosphere-Ionosphere-Plasmasphere (CTIP) model. SAPS events are simulated by imposing a poleward electric field for 2 hours in the premidnight sector between 50° and 60° magnetic latitude. The presence of the SAPS results in a decrease in vertical total electron count and F region ion density, while the height of the F region can rise by up to 100 km. A study of the relative importance of the physical processes finds that the most significant contribution is the temperature increase due to ion-neutral friction, resulting in increased reaction rates of O+ loss. The recovery time for the SAPS studied is up to 10 hours.
BibTeX:
@article{JGRA:JGRA18208,
  author = {Pintér, B. and Thom, S. D. and Balthazor, R. and Vo, H. and Bailey, G. J.},
  title = {Modeling subauroral polarization streams equatorward of the plasmapause footprints},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2006},
  volume = {111},
  number = {A10},
  pages = {n/a--n/a},
  url = {http://dx.doi.org/10.1029/2005JA011457},
  doi = {10.1029/2005JA011457}
}
Luan X, Liu L, Wan W, Lei J, Zhang S-R, Holt JM and Sulzer MP (2006), "A study of the shape of topside electron density profile derived from incoherent scatter radar measurements over Arecibo and Millstone Hill", Radio Science. Vol. 41(4), pp. n/a-n/a.
Abstract: The shape of the topside electron density (Ne) profile is studied using incoherent scatter radar (ISR) measurements. On the basis of more than 90,000 and 84,000 Ne profiles measured over Arecibo (18.4°N, 66.7°W, dip 49.7°) and Millstone Hill (42.6°N, 71.5°W, dip 71.6°), respectively, shape factors have been derived by fitting the ISR observed profile using a Chapman-type layer with a height-independent scale height. The results reveal that the shape factor shows a general departure from the typically used values of 0.5 (Chapman ? layer) except during the night and also undergoes appreciable variation with local time, season, solar activity, and latitude. Over Arecibo, the averaged shape factor is characterized by a daytime maximum of ?0.55–0.75, a nearly constant nighttime value close to 0.5, and a marked morning decline; over Millstone Hill, the shape factor shows pronounced seasonal variations, and the diurnal variation in summer is opposite to that in other seasons. Over both stations, the shape factor exhibits a high correlation with the F2 layer peak electron density (NmF2), and it has strong solar cycle dependence during the late morning hours. It indicates that the temperature structure of the topside ionosphere can explain much of the variation of the shape factor when the plasma density is low, especially during nighttime. During daytime hours, the topside shape factor is thought to be associated with ion-neutral drag during periods of large plasma density.
BibTeX:
@article{Luan2006,
  author = {Luan, Xiaoli and Liu, Libo and Wan, Weixing and Lei, Jiuhou and Zhang, Shun-Rong and Holt, John M. and Sulzer, Michael P.},
  title = {A study of the shape of topside electron density profile derived from incoherent scatter radar measurements over Arecibo and Millstone Hill},
  journal = {Radio Science},
  year = {2006},
  volume = {41},
  number = {4},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2005RS003367},
  doi = {10.1029/2005RS003367}
}
Martinis C, Baumgardner J, Smith SM, Colerico M and Mendillo M (2006), "Imaging science at El Leoncito, Argentina", Annales Geophysicae. Vol. 24(5), pp. 1375-1385.
BibTeX:
@article{Martinis2006,
  author = {Martinis, C. and Baumgardner, J. and Smith, S. M. and Colerico, M. and Mendillo, M.},
  title = {Imaging science at El Leoncito, Argentina},
  journal = {Annales Geophysicae},
  year = {2006},
  volume = {24},
  number = {5},
  pages = {1375-1385},
  doi = {10.5194/angeo-24-1375-2006}
}
Mika A, Haldoupis C, Neubert T, Su HT, Hsu RR, Steiner RJ and Marshall RA (2006), "Early VLF perturbations observed in association with elves", Annales Geophysicae. Vol. 24(8), pp. 2179-2189.
BibTeX:
@article{Mika2006,
  author = {Mika, A. and Haldoupis, C. and Neubert, T. and Su, H. T. and Hsu, R. R. and Steiner, R. J. and Marshall, R. A.},
  title = {Early VLF perturbations observed in association with elves},
  journal = {Annales Geophysicae},
  year = {2006},
  volume = {24},
  number = {8},
  pages = {2179-2189},
  doi = {10.5194/angeo-24-2179-2006}
}
Nicolls MJ, Sulzer MP, Aponte N, Seal R, Nikoukar R and Gonzalez SA (2006), "High-resolution electron temperature measurements using the plasma line asymmetry", Geophysical Research Letters. Vol. 33(18), pp. n/a-n/a.
Abstract: In this paper, we present the first results of a new technique for measuring the electron temperature in the daytime ionosphere using the Arecibo incoherent scatter radar (ISR). The technique utilizes the plasma line component of the incoherent scatter spectrum. The difference in the up- and down-shifted plasma line frequencies is related to the density and temperature of the ionosphere, as well as more minor effects resulting from photoelectrons, currents, and other sources. The shift is very small (the order of 1 kHz in a plasma line frequency of several MHz) but can be measured quite accurately with the coded long pulse plasma line technique. We compare the results to ion line measurements of the electron temperature, and the two independent techniques show good agreement. In addition to providing a measure of the electron temperature that is independent of the ion line, the approach allows for a sensitive test of kinetic plasma theory including a magnetic field, gives us the ability to study photoelectron populations and electron currents, and will allow us to constrain ion line fits in the bottomside (and possibly topside) regions to more accurately fit for composition.
BibTeX:
@article{Nicolls2006,
  author = {Nicolls, M. J. and Sulzer, M. P. and Aponte, N. and Seal, R. and Nikoukar, R. and Gonzalez, S. A.},
  title = {High-resolution electron temperature measurements using the plasma line asymmetry},
  journal = {Geophysical Research Letters},
  year = {2006},
  volume = {33},
  number = {18},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2006GL027222},
  doi = {10.1029/2006GL027222}
}
Nicolls MJ, Aponte N, Gonzalez SA, Sulzer MP and Oliver WL (2006), "Daytime F region ion energy balance at Arecibo for moderate to high solar flux conditions", Journal of Geophysical Research: Space Physics. Vol. 111(A10), pp. A10307 (16 pages).
Abstract: Ion energy balance studies using incoherent scatter radar (ISR) data involve the estimation of the neutral density and exospheric temperature from the ISR-measured parameters using theoretical collision cross sections. The ratio [O]radar/[O]MSIS in long-term averages is an estimate of the so-called Burnside factor and can be derived from these studies. This parameter is thought to be associated with errors in the O+-O collision cross section. The most recent comparison between the Mass Spectrometer Incoherent Scatter (MSIS) neutral atomic oxygen densities and values derived from Arecibo ISR measurements using ion energy balance shows large discrepancies for high solar flux conditions. In contrast to ion momentum studies, which typically lead to a Burnside factor greater than 1 (usually near 1.2–1.3), the discrepancies between MSIS densities and radar-derived values tend to result in low values (near 0.8) for the Burnside factor. Various interpretations of this discrepancy have been put forward. We have reanalyzed the Arecibo ISR World Day data from 1988 to 1994, corresponding to the moderate to high solar flux period of solar cycle 22. By extending the analysis to the upper F region/lower topside (and explicitly including the role of H+, which is often neglected) we obtain consistent results for the neutral density and exospheric temperature that show no significant long-term discrepancy from the MSIS predictions. For this period, we obtain a median ratio [O]radar/[O]MSIS of 1.26 ± 0.02 using the O+-O collision cross section from Banks (1966). The standard deviation of the data is about 0.35. This ratio is close to the most recently published theoretical simulations of the collision cross section within the uncertainties. Knowing the correct O+-O collision cross section allows one to extract the neutral parameters from the radar data and study short-term (day-to-day) variations in those parameters.
BibTeX:
@article{Nicolls2006a,
  author = {Nicolls, Michael J. and Aponte, Néstor and Gonzalez, Sixto A. and Sulzer, Michael P. and Oliver, William L.},
  title = {Daytime F region ion energy balance at Arecibo for moderate to high solar flux conditions},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2006},
  volume = {111},
  number = {A10},
  pages = {A10307 (16 pages)},
  url = {http://dx.doi.org/10.1029/2006JA011664},
  doi = {10.1029/2006JA011664}
}
Pavlov AV, Fukao S and Kawamura S (2006), "A modeling study of ionospheric F2-region storm effects at low geomagnetic latitudes during 17-22 March 1990", Annales Geophysicae. Vol. 24(3), pp. 915-940.
BibTeX:
@article{Pavlov2006,
  author = {Pavlov, A. V. and Fukao, S. and Kawamura, S.},
  title = {A modeling study of ionospheric F2-region storm effects at low geomagnetic latitudes during 17-22 March 1990},
  journal = {Annales Geophysicae},
  year = {2006},
  volume = {24},
  number = {3},
  pages = {915-940},
  doi = {10.5194/angeo-24-915-2006}
}
Pavlov AV (2006), "The role of the zonal E&times;B plasma drift in the low-latitude ionosphere at high solar activity near equinox from a new three-dimensional theoretical model", Annales Geophysicae. Vol. 24(10), pp. 2553-2572.
BibTeX:
@article{Pavlov2006a,
  author = {Pavlov, A. V.},
  title = {The role of the zonal E&times;B plasma drift in the low-latitude ionosphere at high solar activity near equinox from a new three-dimensional theoretical model},
  journal = {Annales Geophysicae},
  year = {2006},
  volume = {24},
  number = {10},
  pages = {2553-2572},
  doi = {10.5194/angeo-24-2553-2006}
}
Waldrop LS, Kudeki E, Gonzalez SA, Sulzer MP, Garcia R, Butala M and Kamalabadi F (2006), "Derivation of neutral oxygen density under charge exchange in the midlatitude topside ionosphere", Journal of Geophysical Research: Space Physics. Vol. 111(A11), pp. n/a-n/a.
BibTeX:
@article{Waldrop2006,
  author = {Waldrop, L. S. and Kudeki, E. and Gonzalez, S. A. and Sulzer, M. P. and Garcia, R. and Butala, M. and Kamalabadi, F.},
  title = {Derivation of neutral oxygen density under charge exchange in the midlatitude topside ionosphere},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2006},
  volume = {111},
  number = {A11},
  pages = {n/a-n/a},
  doi = {10.1029/2005JA011496}
}
Zhou Q and Morton YT (2006), "A case study of mesospheric gravity wave momentum flux and dynamical instability using the Arecibo dual beam incoherent scatter radar", Geophysical Research Letters. Vol. 33(10), pp. L10802 (4 pages).
Abstract: We report the first observation of gravity wave momentum flux in the mesosphere using the dual-beam Arecibo incoherent scatter radar (ISR). Quasi-monochromatic waves were observed throughout the daytime of July 28, 2001 in the altitude range of 65–85 km. The largest wave speed was about 100 m/s and the dominant period was about 15 min. Instability, as indicated by the Richardson number, occurred at several altitudes, most dramatically at 77 and 81 kilometers. The zonal momentum flux is found to change sign at altitudes where dynamical instability occurs. No significant gravity waves were observed in the region having an eastward background wind, while they were ubiquitous when the background wind was westward.
BibTeX:
@article{Zhou2006,
  author = {Zhou, Qihou and Morton, Y. T.},
  title = {A case study of mesospheric gravity wave momentum flux and dynamical instability using the Arecibo dual beam incoherent scatter radar},
  journal = {Geophysical Research Letters},
  year = {2006},
  volume = {33},
  number = {10},
  pages = {L10802 (4 pages)},
  url = {http://dx.doi.org/10.1029/2005GL025608},
  doi = {10.1029/2005GL025608}
}
Raizada S (2006), "Research Experience for Undergraduates Program, PROGRESS REPORT SUMMER 2006"
BibTeX:
@techreport{,
  author = {Shikha Raizada},
  title = {Research Experience for Undergraduates Program, PROGRESS REPORT SUMMER 2006},
  year = {2006}
}
Abdu M, Batista I, Carrasco A and Brum C (2005), "South Atlantic magnetic anomaly ionization: A review and a new focus on electrodynamic effects in the equatorial ionosphere ", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 67(17-18), pp. 1643 - 1657.
Abstract: Satellite observations of enhanced energetic particle fluxes in the South Atlantic Magnetic Anomaly (SAMA) region have been supported by ground-based observations of enhanced ionization induced by particle precipitation in the ionosphere over this region. Past observations using a variety of instruments such as vertical sounding ionosondes, riometers and VLF receivers have provided evidences of the enhanced ionization due to energetic particle precipitation in the ionosphere over Brazil. The extra ionization at E-layer heights could produce enhanced ionospheric conductivity within and around the SAMA region. The energetic particle ionization source that is operative even under “quiet” conditions can undergo significant enhancements during magnetospheric storm disturbances, when the geographic region of enhanced ionospheric conductivity can extend to magnetic latitudes closer to the equator where the magnetic field line coupling of the E and F regions plays a key role in the electrodynamics of the equatorial ionosphere. Of particular interest are the sunset electrodynamic processes responsible for equatorial spread F/plasma bubble irregularity generation and related dynamics (zonal and vertical drifts, etc.). The SAMA represents a source of significant longitudinal variability in the global description of the equatorial spread F irregularity phenomenon. Recent results from digital ionosondes operated at Fortaleza and Cachoeira Paulista have provided evidence that enhanced ionization due to particle precipitation associated with magnetic disturbances, in the SAMA region, can indeed significantly influence the equatorial electrodynamic processes leading to plasma irregularity generation and dynamics. Disturbance magnetospheric electric fields that penetrate the equatorial latitudes during storm events seem to be intensified in the SAMA region based on ground-based and satellite-borne measurements. This paper will review our current understanding of the influence of SAMA on the equatorial electrodynamic processes from the perspective outlined above.
BibTeX:
@article{Abdu2005,
  author = {M.A. Abdu and I.S. Batista and A.J. Carrasco and C.G.M. Brum},
  title = {South Atlantic magnetic anomaly ionization: A review and a new focus on electrodynamic effects in the equatorial ionosphere },
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2005},
  volume = {67},
  number = {17-18},
  pages = {1643 - 1657},
  note = {Arecibo author},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682605001240},
  doi = {10.1016/j.jastp.2005.01.014}
}
Aponte N, Nicolls MJ, Gonzales SA, Sulzer MP, Kelley MC, Robles E and Tepley CA (2005), "Instantaneous electric field measurements and derived neutral winds at Arecibo", Geophysical Research Letters. Vol. 32(12), pp. n/a-n/a.
Abstract: Previously, ion vector velocity measurements at Arecibo required the rotation of the antenna (a 360° rotation takes about 15 minutes) in order to accumulate enough information from different directions. In addition, a least-squares fitting method or a more sophisticated inversion technique is necessary to determine horizontal velocities. This study reports the first instantaneous long-duration F region vector velocity measurements in the magnetic meridian plane using the dual-beam system. This configuration is suitable for measuring the eastward electric field and deriving the meridional neutral wind with very high time resolution. The first results of this experiment presented here seem to show evidence for a gravity wave driven plasma process.
BibTeX:
@article{Aponte2005,
  author = {Aponte, Nestor and Nicolls, Michael J. and Gonzales, Sixto A. and Sulzer, M. P. and Kelley, Michael C. and Robles, Eva and Tepley, Craig A.},
  title = {Instantaneous electric field measurements and derived neutral winds at Arecibo},
  journal = {Geophysical Research Letters},
  year = {2005},
  volume = {32},
  number = {12},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2005GL022609},
  doi = {10.1029/2005GL022609}
}
Bhat NDR, Cordes JM, Chatterjee S and Lazio TJW (2005), "Radio frequency interference identification and mitigation using simultaneous dual-station observations", Radio Science. Vol. 40(5), pp. n/a-n/a.
Abstract: Radio frequency interference (RFI) mitigation is a critically important issue in radio astronomy using existing instruments as well as in the development of next generation radio telescopes, such as the Square Kilometer Array (SKA). Most designs for the SKA involve multiple stations with spacings of up to a few thousands of kilometers and thus can exploit the drastically different RFI environments at different stations. As demonstrator observations and analysis for SKA-like instruments, and to develop RFI mitigation schemes that will be useful in the near term, we recently conducted simultaneous observations with Arecibo Observatory and the Green Bank Telescope. The observations were aimed at diagnosing RFI and using the mostly uncorrelated RFI between the two sites to excise RFI from several generic kinds of measurements such as giant pulses from Crab-like pulsars and weak H I emission from galaxies in bands heavily contaminated by RFI. This paper presents observations, analysis, and RFI identification and excision procedures that are effective for both time series and spectroscopy applications using multistation data.
BibTeX:
@article{Bhat2005,
  author = {Bhat, N. D. R. and Cordes, J. M. and Chatterjee, S. and Lazio, T. J. W.},
  title = {Radio frequency interference identification and mitigation using simultaneous dual-station observations},
  journal = {Radio Science},
  year = {2005},
  volume = {40},
  number = {5},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2004RS003172},
  doi = {10.1029/2004RS003172}
}
Contreira D, Rodrigues F, Makita K, Brum C, Gonzalez W, Trivedi N, da Silva M and Schuch N (2005), "An experiment to study solar flare effects on radio-communication signals ", Advances in Space Research . Vol. 36(12), pp. 2455-2459.
Abstract: The occurrence of radio signal fading events caused by ionospheric absorption plays an important role in the performance of radio-communication systems. It is necessary to know the magnitude and time-scale of such events in order to specify technical parameters of the communication system to be used. Generally, fading events are associated with solar flares, which are characterized by sudden increase in the solar X-ray flux that causes an increase in the ionization in the lower ionosphere. The abrupt increase of ionization causes the absorption of radio waves propagating in the Earth–ionosphere wave-guide and is reported as radio signal fading events. A simple experiment to monitor the behavior of lower ionosphere has been carried out at the Southern Space Observatory-SSO/INPE (29.43S, 53.8W), located in southern Brazil. The experiment is basically a computer controlled radio receiver that records the received signal strength of Amplitude Modulated (AM) radio signals in the HF (High Frequencies) range. We analyzed data of the 6MHz beacon signal that has been transmitted by a broadcasting radio station located about 400;km from the observation site. In this work we present initial results of daily variation of the received signal strength and fading events associated with solar flares observed in the 6MHz signal monitored by the experiment during 2001. X-ray solar flux data from the GOES-8 satellite were used to identify X-ray solar bursts associated with solar flares. Based on the one-year data collected by the experiment, a statistical summary of fading occurrences and their correlation with solar flares, as well as the distributions of time-scales and magnitudes of such events are presented.
BibTeX:
@article{Contreira2005,
  author = {D.B. Contreira and F.S. Rodrigues and K. Makita and C.G.M. Brum and W. Gonzalez and N.B. Trivedi and M.R. da Silva and N.J. Schuch},
  title = {An experiment to study solar flare effects on radio-communication signals },
  journal = {Advances in Space Research },
  year = {2005},
  volume = {36},
  number = {12},
  pages = {2455-2459},
  note = {Arecibo author},
  url = {http://www.sciencedirect.com/science/article/pii/S027311770500013X},
  doi = {10.1016/j.asr.2004.03.019}
}
González JE, Luvall JC, Rickman D, Comarazamy D, Picón A, Harmsen E, Parsiani H, Vásquez RE, Ramírez N, Williams R, Waide RW and Tepley CA (2005), "Urban heat islands developing in coastal tropical cities", Eos, Transactions American Geophysical Union. Vol. 86(42), pp. 397-403.
Abstract: Beautiful and breezy cities on small tropical islands, it turns out, may not be exempt from the same local climate change effects and urban heat island effects seen in large continental cities such as Los Angeles or Mexico City. A surprising, recent discovery indicates that this is the case for San Juan, Puerto Rico, a relatively affluent coastal tropical city of about two million inhabitants that is spreading rapidly into the once-rural areas around it.A recent climatological analysis of the surface temperature of the city has revealed that the local temperature has been increasing over the neighboring vegetated areas at a rate of 0.06°C per year for the past 30 years. This is a trend that may be comparable to climate changes induced by global warming.
BibTeX:
@article{EOST:EOST15258,
  author = {González, Jorge E. and Luvall, Jeffrey C. and Rickman, Douglas and Comarazamy, Daniel and Picón, Ana and Harmsen, Eric and Parsiani, Hamed and Vásquez, Ramón E. and Ramírez, Nazario and Williams, Robin and Waide, Robert W. and Tepley, Craig A.},
  title = {Urban heat islands developing in coastal tropical cities},
  journal = {Eos, Transactions American Geophysical Union},
  year = {2005},
  volume = {86},
  number = {42},
  pages = {397--403},
  url = {http://dx.doi.org/10.1029/2005EO420001},
  doi = {10.1029/2005EO420001}
}
Friedman JS and Janches D (2005), "Special issue on meteors and the mesopause ", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 67(13), pp. 1157 - 1158.
Abstract: The study of meteors has developed new relevance in recent years. This has been motivated by scientific interests as mundane as meteor ablation processes and the chemistry and state of the middle atmosphere, as fundamental as the origins and evolution of the earth and its environment and life, and as sublime as the possibility that life exists or existed elsewhere in the solar system or the galaxy. Motivation has also come from new techniques for recording the characteristics of meteor trails, using radar, optics, and ultrasound, and the new information these techniques have provided. This special issue contains a collection of papers that address the “mundane” of these issues, yet the conclusions are of fundamental importance to the study of the earth and its celestial environs. They deal with how and where meteoric material is deposited in the atmosphere and the chemistry that follows in order to form the metal layers in the mesosphere and lower thermosphere. It should be noted that we address issues that involve only the small portion of the total meteoric mass input ( ? g –g particles) that is responsible for the phenomena discussed. We do not address meteorites, bolides, and other large objects.
BibTeX:
@article{Friedman20051157,
  author = {Jonathan S. Friedman and Diego Janches},
  title = {Special issue on meteors and the mesopause },
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2005},
  volume = {67},
  number = {13},
  pages = {1157 - 1158},
  note = {Meteors and the MesopauseMeteors and the Mesopause },
  url = {http://www.sciencedirect.com/science/article/pii/S1364682605001045},
  doi = {10.1016/j.jastp.2005.06.001}
}
Goncharenko LP, Salah JE, van Eyken A, Howells V, Thayer JP, Taran VI, Shpynev B, Zhou Q and Chau J (2005), "Observations of the April 2002 geomagnetic storm by the global network of incoherent scatter radars", Annales Geophysicae. Vol. 23(1), pp. 163-181.
Abstract: This paper describes the ionospheric response to a geomagnetic storm beginning on 17 April 2002. We present the measurements of ionospheric parameters in the F-region obtained by the network of eight incoherent scatter radars. The main effects of this storm include a deep decrease in the electron density observed at high and middle latitudes in the pre-noon sector, and a minor enhancement in the density observed in the daytime sector at middle latitudes. Extreme plasma heating (>1000-3000 K) is observed at high latitudes, subsiding to 200-300K at subauroral latitudes. The western hemisphere radar chain observed the prompt penetration of the electric field from auroral to equatorial latitudes, as well as the daytime enhancement of plasma drift parallel to the magnetic field line, which is related to the enhancement in the equatorward winds. We suggest that in the first several hours after the storm onset, a negative phase above Millstone Hill (pre-noon sector) results from counteracting processes - penetration electric field, meridional wind, and electrodynamic heating, with electrodynamic heating being the dominant mechanism. At the lower latitude in the pre-noon sector (Arecibo and Jicamarca), the penetration electric field becomes more important, leading to a negative storm phase over Arecibo. In contrast, in the afternoon sector at mid-latitudes (Kharkov, Irkutsk), effects of penetration electric field and meridional wind do not counteract, but add up, leading to a small (~15%), positive storm phase over these locations. As the storm develops, Millstone Hill and Irkutsk mid-latitude radars observe further depletion of electron density due to the changes in the neutral composition.
BibTeX:
@article{Goncharenko2005,
  author = {Goncharenko, L. P. and Salah, J. E. and van Eyken, A. and Howells, V. and Thayer, J. P. and Taran, V. I. and Shpynev, B. and Zhou, Q. and Chau, J.},
  title = {Observations of the April 2002 geomagnetic storm by the global network of incoherent scatter radars},
  journal = {Annales Geophysicae},
  year = {2005},
  volume = {23},
  number = {1},
  pages = {163-181},
  doi = {10.5194/angeo-23-163-2005}
}
Gonzalez SA, Nicolls MJ, Sulzer MP and Aponte N (2005), "An energy balance study of the lower topside ionosphere using the Arecibo incoherent scatter radar and heating facilities", Journal of Geophysical Research: Space Physics. Vol. 110(A11), pp. n/a-n/a.
Abstract: In this paper we describe the results of an experiment to study electron and ion temperature enhancements during an HF modification experiment at the Arecibo Observatory. This experiment is unique in that we pointed the radar away from the interaction region in the F region in order to study heat conduction along the field lines. Although electron temperature enhancements have been frequently observed when high-power radio waves are injected into the ionosphere, observations generally have occurred in the interaction region and the regions of elevated electron temperatures have been accompanied by small ion temperature increases (50–200 K). Like many such experiments, this one was conducted during winter solar minimum, when f0F2 is low during the night at midlatitudes, but this experiment also had the advantage of the upgraded Arecibo HF facility, first used in 1997. The electron temperature enhancements were accompanied by a significant increase in the ion temperature (nearly 500 K). The observation away from the interaction region allowed the application of the time-dependent heating equation without having to estimate local heating effects (i.e., by keeping the conduction and loss terms in the energy balance calculation and neglecting the source term). More specifically, the heating rate of conduction was quantified by manipulating the heat equation. Thus the primary purpose was to observe the temperatures as the heat was conducted away from the F region ionosphere. We have observed the gradients in the electron temperature caused by the heater, estimated the conduction along the field lines, and studied the transfer of energy from the hot electrons to the ions and neutrals. At lower altitudes, near the electron-temperature peak, we show that O+ cooling is dominant, whereas in the lower topside H+ cooling is the most important. Experiments of the type described here could be enhanced with the new dual-beam system at Arecibo in conjunction with a heating facility.
BibTeX:
@article{Gonzalezs2005,
  author = {Gonzalez, S A. and Nicolls, Michael J. and Sulzer, Michael P. and Aponte, Nestor},
  title = {An energy balance study of the lower topside ionosphere using the Arecibo incoherent scatter radar and heating facilities},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2005},
  volume = {110},
  number = {A11},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2005JA011154},
  doi = {10.1029/2005JA011154}
}
Höffner J and Friedman J (2005), "The mesospheric metal layer topside: Examples of simultaneous metal observations ", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 67(13), pp. 1226 - 1237.
Abstract: We show examples of common volume observations of three metals by lidar focusing on the altitude of the topside of the meteoric metal layer as described by Höffner and Friedman (H&amp;F) [The mesospheric metal layer topside: a possible connection to meteoroids, Atmos. Chem. Phys. 4 (2004) 801–808]. In contrast to H&amp;F, we will focus on time scales of a few hours and less whereas the previous study examined the seasonally averaged climatological state on time scales of several days or weeks, and we examine the entire topside, whereas H&amp;F focused on data at 113 km. The examples, taken under different observation conditions in 1997 and 1998 at Kühlungsborn, Germany (54°N, 15°E), show that the metal layers can often be observed at altitudes as high as 130 km if the signal is integrated over a period of several hours. Under such conditions it is possible to derive reasonably good metal abundance ratios from nocturnally averaged data, which, in turn, allow the discussion of metal abundance ratios to broaden from a single altitude as discussed in H&amp;F to an altitude range extending as high as 130 km. The examples herein show, for the first time, that it is possible to track the transition in the metal abundance ratios from the main layer to an altitude region that has not been studied in the past by lidar. On shorter time scales, small structures are detectable and observable, sometimes above 120 km, resulting in, on average, a broad but weak topside layer above 105 km. In particular, the example of 26–27 October 1997, obtained during enhanced meteor activity, is an indication that this broad layer may result from meteor ablation occurring in this altitude range during the observation. Ratios of metal densities for Ca, Fe, K, and Na are remarkably consistent above about 110 km and in close agreement with the results of H&amp;F. They are less consistent with ratios measured in individual meteor trails and appear to have little relation to the ratios measured in CI meteorites. Finally, it is the temporal smoothing of descending sporadic metal atom layers on top of an undisturbed background metal layer that is the basis of the summer topside extension as described by H&amp;F.
BibTeX:
@article{Höffner20051226,
  author = {J. Höffner and J.S. Friedman},
  title = {The mesospheric metal layer topside: Examples of simultaneous metal observations },
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2005},
  volume = {67},
  number = {13},
  pages = {1226 - 1237},
  note = {Meteors and the MesopauseMeteors and the Mesopause },
  url = {http://www.sciencedirect.com/science/article/pii/S1364682605001148},
  doi = {10.1016/j.jastp.2005.06.010}
}
Janches D and ReVelle DO (2005), "Initial altitude of the micrometeor phenomenon: Comparison between Arecibo radar observations and theory", Journal of Geophysical Research: Space Physics. Vol. 110(A8), pp. n/a-n/a.
Abstract: We present calculations of the altitude at which the micrometeor phenomenon begins, that is, the point where the interaction between micrometeoroids and the Earth's atmosphere becomes important. At these altitudes, physical processes such as light emission, heating, electron production, etc., begin to occur. The calculations are performed using four very different initial height models including (1) solving the full integration of the single-body meteor equations, (2) using a balance between the loss of momentum and the component of the acceleration due to gravity along the meteor trajectory, (3) using a solution that emanates from a “linearized” form of the meteor energy equation but without including either atmosphere or meteoroid radiation emission effects, and finally (4) utilizing a solution of the meteor energy equation that is specifically approximated for small particles. We compare our evaluated theoretical results with direct micrometeor observations detected using the 430 MHz Arecibo Observatory (AO) radar system. The goal of these calculations is to provide reliable initial conditions in order to completely model the AO micrometeor observations, most of which have nearly constant decelerations. The nature of this study, although performed with already existing theoretical formulations, is of unprecedented value because it is the first study where these models are directly compared against very highly resolved micrometeor velocity and altitude distributions that are derived directly from the radar observations. We found that the meteor energy equation approximated for small particles agrees very well with the radar observations, in particular for meteor melting temperatures of the order of 2100 K and entry angles lower than 30° with respect to the radar beam normal direction. Unfortunately, from this model the composition characteristics of the particles detected by the AO radar cannot conclusively be drawn. However, comparison with the calculation of the penetration height of meteoroids reported by ReVelle (2005a) suggests that chondritic material seem to be the best candidate to explain the observed penetration of these particles in the mesosphere. Calculation of the light emission and electron density production of the meteor are also presented and discussed.
BibTeX:
@article{Janches2005,
  author = {Janches, Diego and ReVelle, Douglas O.},
  title = {Initial altitude of the micrometeor phenomenon: Comparison between Arecibo radar observations and theory},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2005},
  volume = {110},
  number = {A8},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2005JA011022},
  doi = {10.1029/2005JA011022}
}
Janches D and Chau J (2005), "Observed diurnal and seasonal behavior of the micrometeor flux using the Arecibo and Jicamarca radars ", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 67(13), pp. 1196-1210.
BibTeX:
@article{Janches2005a,
  author = {D. Janches and J.L. Chau},
  title = {Observed diurnal and seasonal behavior of the micrometeor flux using the Arecibo and Jicamarca radars },
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2005},
  volume = {67},
  number = {13},
  pages = {1196-1210},
  doi = {10.1016/j.jastp.2005.06.011}
}
Harmon JK and Coles WA (2005), "Modeling radio scattering and scintillation observations of the inner solar wind using oblique Alfvén/ion cyclotron waves", Journal of Geophysical Research: Space Physics. Vol. 110(A3), pp. n/a-n/a.
Abstract: Radio scattering and scintillation observations of the near-Sun solar wind are shown to be dominated by effects associated with obliquely propagating Alfvén/ion cyclotron waves. We base this on a modeling of structure functions from angular/spectral broadening observations and velocity measurements from interplanetary scintillation (IPS) observations. A simple damped-WKB model was found inadequate, as Landau damping erodes the spectrum faster than is consistent with the observed inner scale. Invoking a turbulent cascade can counteract this damping and push the spectral cutoff back out to the observed inner scale near the ion inertial scale. Adjusting the spectrum amplitude and cascade rate to match observations gives an estimate of the wave dissipation power associated with electron Landau damping and proton cyclotron damping. The implied power levels are substantial, being comparable with levels typically invoked in extended wave heating models. Both the shape and the amplitude of the observed structure functions can be explained by a composite spectrum made up of a power law component of passive or non-Alfvénic density fluctuations and a local flattening associated with the enhanced linear Alfvén wave compressibility at small (ion cyclotron) scales. Since IPS is dominated by the enhanced small-scale density fluctuations, the scintillation velocity field should show a strong wave effect. Our modeling of IPS velocities does, in fact, show that the large parallel velocity spread and upward bias to the mean velocity observed near the Sun are a direct result of the density fluctuations associated with Alfvén waves along an extended line of sight.
BibTeX:
@article{JGRA:JGRA17735,
  author = {Harmon, John K. and Coles, William A.},
  title = {Modeling radio scattering and scintillation observations of the inner solar wind using oblique Alfvén/ion cyclotron waves},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2005},
  volume = {110},
  number = {A3},
  pages = {n/a--n/a},
  url = {http://dx.doi.org/10.1029/2004JA010834},
  doi = {10.1029/2004JA010834}
}
Kuo SP and Lee MC (2005), "Cascade spectrum of HF enhanced plasma lines generated in HF heating experiments", Journal of Geophysical Research: Space Physics. Vol. 110(A1), pp. n/a-n/a.
BibTeX:
@article{Kuo2005,
  author = {Kuo, S. P. and Lee, M. C.},
  title = {Cascade spectrum of HF enhanced plasma lines generated in HF heating experiments},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2005},
  volume = {110},
  number = {A1},
  pages = {n/a-n/a},
  doi = {10.1029/2004JA010674}
}
Martin JD, Morton YT and Zhou Q (2005), "Neural network development for the forecasting of upper atmosphere parameter distributions ", Advances in Space Research . Vol. 36(12), pp. 2480-2485.
BibTeX:
@article{Martin2005,
  author = {Jeffrey D. Martin and Yu T. Morton and Qihou Zhou},
  title = {Neural network development for the forecasting of upper atmosphere parameter distributions },
  journal = {Advances in Space Research },
  year = {2005},
  volume = {36},
  number = {12},
  pages = {2480-2485},
  doi = {10.1016/j.asr.2003.12.015}
}
Nicolls MJ and Kelley MC (2005), "Strong evidence for gravity wave seeding of an ionospheric plasma instability", Geophysical Research Letters. Vol. 32(5), pp. n/a-n/a.
Abstract: Here we present evidence for gravity wave seeding of ionospheric plasma instabilities. On October 2, 2002 a series of magnetic substorms led to a large-scale traveling ionospheric disturbance (LSTID) that was detected by the Arecibo incoherent scatter radar. Several large oscillations of the F layer occurred, including one that lifted the layer to over 450 km. At least two shorter period oscillations were identified in the plasma contours along the bottomside of the layer. The largest amplitude signal exhibited a downward phase velocity, vertical wavelength, and period (~50 minutes) consistent with the linear theory of gravity waves. A ~30-minute period oscillation was amplified considerably when the bottomside was lifted to high altitudes near dawn. This amplification was likely due to a gravitational instability with a growth time of about 15 minutes. We believe that the LSTID created conditions conducive to instability, while the shorter period waves created the seed irregularities.
BibTeX:
@article{Nicolls2005,
  author = {Nicolls, Michael J. and Kelley, Michael C.},
  title = {Strong evidence for gravity wave seeding of an ionospheric plasma instability},
  journal = {Geophysical Research Letters},
  year = {2005},
  volume = {32},
  number = {5},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2004GL020737},
  doi = {10.1029/2004GL020737}
}
Pellinen-Wannberg A (2005), "Meteor head echoes - observations and models", Annales Geophysicae. Vol. 23, pp. 201-205.
BibTeX:
@article{Pellinen-Wannberg2005,
  author = {Pellinen-Wannberg, A},
  title = {Meteor head echoes - observations and models},
  journal = {Annales Geophysicae},
  year = {2005},
  volume = {23},
  pages = {201-205},
  doi = {10.5194/angeo-23-201-2005}
}
Petitdidier M and Laroche P (2005), "Lightning observations with the Strato-Tropospheric UHF and VHF radars at Arecibo, Puerto Rico", Atmospheric Research. Vol. 76(1-4), pp. 481-492.
Abstract: Observations were carried out at National Astronomy and Ionospheric Center (NAIC) in Puerto Rico with a dual-frequency (46.8MHz/430MHz) Strato-Tropospheric radar associated with ground-based precipitation and electrostatic field measurements. This experimental set-up is devoted to provide wind measurements and detection of clear air turbulence. During a thunderstorm event, VHF-UHF radar receivers detected wide frequency band radiation emitted by lightning flashes. We present in this paper observations of a specific storm for which lightning radiation and ionized lightning channel were fortuitously and simultaneously detected. A bi-level structure of the lightning flash channel is observed and is consistent with observations obtained previously by other authors with VHF lightning mapper.
BibTeX:
@article{Petitdidier2005,
  author = {Petitdidier, M and Laroche, P},
  title = {Lightning observations with the Strato-Tropospheric UHF and VHF radars at Arecibo, Puerto Rico},
  journal = {Atmospheric Research},
  year = {2005},
  volume = {76},
  number = {1-4},
  pages = {481-492},
  url = {http://www.sciencedirect.com/science/article/pii/S0169809505000724},
  doi = {10.1016/j.atmosres.2004.11.037}
}
Deshpande AA (2005), "Correlations of spectral intensity fluctuations: Application to radio frequency interference mitigation", Radio Science. Vol. 40(5), pp. n/a-n/a.
Abstract: This paper describes a technique based on correlating fluctuations in spectral intensities. When applied to intensity data recorded as a function of time and frequency, the result can be viewed in the form of a correlation map, wherein the temporal correlation between fluctuations in every possible pair of spectral channels is represented. In addition to serving as a useful diagnostic tool for the measuring system itself, such a correlation map offers a wealth of information on spectral channels affected by radio frequency interference (RFI) and intermodulation products, if any. Although such estimations are inherently less sensitive than those using voltage correlations, the technique promises much broader applicability since intensity data are more commonly available. The strengths and weaknesses of this technique with respect to RFI mitigation are discussed and are illustrated with real examples. An extension of this analysis to polarization data is also explored. A promising way to isolate RFI on the basis of its highly polarized nature is proposed, and relevant practical issues are discussed. The present study suggests that high-resolution time-frequency data for the full Stokes parameters allow effective excision of RFI (by typically more than 20 dB), particularly for observations of unpolarized astronomical sources. This method is exceedingly effective in situations where a large fraction of the data is affected by polarized RFI, where a robust statistics approach fails.
BibTeX:
@article{RDS:RDS5154,
  author = {Deshpande, Avinash A.},
  title = {Correlations of spectral intensity fluctuations: Application to radio frequency interference mitigation},
  journal = {Radio Science},
  year = {2005},
  volume = {40},
  number = {5},
  pages = {n/a--n/a},
  url = {http://dx.doi.org/10.1029/2004RS003156},
  doi = {10.1029/2004RS003156}
}
ReVelle D (2005), "The Mesopause as a physical penetration boundary", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 67(13), pp. 1159-1170.
BibTeX:
@article{ReVelle2005,
  author = {D.O. ReVelle},
  title = {The Mesopause as a physical penetration boundary},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2005},
  volume = {67},
  number = {13},
  pages = {1159-1170},
  doi = {10.1016/j.jastp.2005.06.002}
}
Roper RG and Brosnahan JW (2005), "Diurnal variations in the rate of dissipation of turbulent energy in the equatorial uppermesosphere–lower thermosphere", Radio Science. Vol. 40(4), pp. n/a-n/a.
BibTeX:
@article{Roper2005,
  author = {Roper, R. G. and Brosnahan, J. W.},
  title = {Diurnal variations in the rate of dissipation of turbulent energy in the equatorial uppermesosphere–lower thermosphere},
  journal = {Radio Science},
  year = {2005},
  volume = {40},
  number = {4},
  pages = {n/a-n/a},
  doi = {10.1029/2004RS003198}
}
Smith S, Friedman J, Raizada S, Tepley C, Baumgardner J and Mendillo M (2005), "Evidence of mesospheric bore formation from a breaking gravity wave event: simultaneous imaging and lidar measurements ", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 67(4), pp. 345 - 356.
Abstract: A large wave event was observed in the three upper-mesospheric (80–105 km) airglow emissions of O(1S), Na and OH by the Boston University all-sky imager, at the Arecibo Observatory, during the night of 3 May 2003. The airglow structures appeared to be due to a large upward propagating internal gravity wave, which subsequently became unstable near the 95 km height level and produced large-scale vertical motions and mixing. Simultaneous density and temperature lidar measurements indicated the presence of a large temperature inversion of 80 K valley-to-peak between 88 and 96 km during the time of the event. Near-simultaneous temperature profiles, made by the TIMED SABER instrument, provided evidence that the horizontal extent of the inversion was localized to within 500 km of Arecibo during the wave event. As the gravity wave dissipated, an internal bore was generated, apparently due to the deposition of momentum and energy into the region by the original wave. Although mesospheric gravity wave breaking has been reported previously (Swenson and Mende, 21(1994); Hecht et al., 102(1997); Yamada et al., 28(2001), for example), this was the first time that the phenomenon has been associated with the generation of an internal mesospheric bore. The event suggested that the breaking of a large mesospheric gravity wave can lead to the generation of an internal bore, as suggested by Dewan and Picard 106(2001). Such behavior is of particular interest since little is known of their origins.
BibTeX:
@article{Smith2005345,
  author = {S.M. Smith and J. Friedman and S. Raizada and C. Tepley and J. Baumgardner and M. Mendillo},
  title = {Evidence of mesospheric bore formation from a breaking gravity wave event: simultaneous imaging and lidar measurements },
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2005},
  volume = {67},
  number = {4},
  pages = {345 - 356},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682604002871},
  doi = {10.1016/j.jastp.2004.11.008}
}
Sulzer MP, Aponte N and Gonzalez SA (2005), "Application of linear regularization methods to Arecibo vector velocities", Journal of Geophysical Research: Space Physics. Vol. 110(A10), pp. n/a-n/a.
Abstract: Estimates of the three-dimensional ion velocity field can be difficult to make with monostatic radars because there are three unknown components for each independent line of sight velocity measurement. To cope with this problem, one or more assumptions about the vector field must be made to arrive at a solution. At Arecibo, one can measure the ion vector velocities by continuously rotating the antenna beam back and forth 360 degrees in azimuth at 15 degrees off zenith to sample the horizontal components. Until recently, the line of sight velocities obtained from this experiment were typically converted into vector velocities by assuming that the vector field remains constant during one rotation and that horizontal gradients are negligible. In this paper we show how to apply the linear regularization inversion method to the problem of computing ion vector velocities. This technique improves the accuracy of the vector velocities obtained from the measured F region line of sight velocities and also provides a convenient way to do the computations for dual-beam experiments. The technique could improve the vector velocities at other monostatic incoherent scatter radar facilities.
BibTeX:
@article{Sulzer2005,
  author = {Sulzer, Michael P. and Aponte, Néstor and Gonzalez, Sixto A.},
  title = {Application of linear regularization methods to Arecibo vector velocities},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2005},
  volume = {110},
  number = {A10},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2005JA011042},
  doi = {10.1029/2005JA011042}
}
Vlasov MN, Nicolls MJ, Kelley MC, Smith SM, Aponte N and Gonzalez SA (2005), "Modeling of airglow and ionospheric parameters at Arecibo during quiet and disturbed periods in October 2002", Journal of Geophysical Research: Space Physics. Vol. 110(A7), pp. n/a-n/a.
Abstract: The main purpose of this paper is to analyze observations of the 630.0-nm (red line) and 557.7-nm (green line) zenith airglow intensities measured during the month of October 2002 over Arecibo, Puerto Rico. We begin by describing an improved model for calculating the intensity of the red and green airglow lines that takes into account the role of molecular ions. We show, however, that at least for the data used in this study, it is not necessary to include the effects of molecular ions in our calculations. From observations of the airglow emissions on quiet days, we infer the general characteristics of the red-line intensities, which show a minimum before midnight and a peak after midnight. These results are consistent with a decrease in NmF2 and an increase in hmF2 before midnight, followed by the so-called “midnight collapse.” We then focus on the storm day of October 1-2, 2002, during which large-amplitude variations in both the red- and green-line intensities were observed and reproduced by the airglow model. An additional peak of NmF2, together with an hmF2 decrease, was observed before midnight, associated with the passage of a large-scale atmospheric gravity wave. The NmF2 nighttime increase requires plasma flux from the plasmasphere, which we find can be as large as 109 cm-2 s-1. The plasmasphere needs an additional source of plasma in order to provide such a large flux, and we explain this by considering the role of the meridional wind in the plasma exchange process. Strong changes in the shape of the F2 region were observed during the downward and upward motion of the F2 layer during the storm period. We have found simple analytical solutions for the height distributions of the electron density in the F2 region by including the effects of recombination and diffusion. These height distributions are in excellent agreement with the measured profiles. Finally, we discuss mesospheric green-line fluctuations and show that good agreement can be obtained for the storm conditions if small adjustments are made to the eddy diffusion coefficients in the mesosphere, which we associate with the passage of the gravity wave. However, we find that some green-line behavior during quiet-time conditions is difficult to explain.
BibTeX:
@article{Vlasov2005,
  author = {Vlasov, Michael N. and Nicolls, Michael J. and Kelley, Michael C. and Smith, Steven M. and Aponte, Nestor and Gonzalez, Sixto A.},
  title = {Modeling of airglow and ionospheric parameters at Arecibo during quiet and disturbed periods in October 2002},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2005},
  volume = {110},
  number = {A7},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2005JA011074},
  doi = {10.1029/2005JA011074}
}
Waldrop LS, Kerr RB, Gonzalez SA, Sulzer MP, Noto J and Kamalabadi F (2005), "Generation of metastable helium and the 1083 nm emission in the upper thermosphere", Journal of Geophysical Research: Space Physics. Vol. 110(A8), pp. n/a-n/a.
BibTeX:
@article{Waldrop2005,
  author = {Waldrop, L. S. and Kerr, R. B. and Gonzalez, S. A. and Sulzer, M. P. and Noto, J. and Kamalabadi, F.},
  title = {Generation of metastable helium and the 1083 nm emission in the upper thermosphere},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2005},
  volume = {110},
  number = {A8},
  pages = {n/a-n/a},
  doi = {10.1029/2004JA010855}
}
Wen C-H, Doherty J, Mathews J and Janches D (2005), "Meteor detection and non-periodic bursty interference removal for Arecibo data ", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 67(3), pp. 275 - 281.
Abstract: Signal processing techniques for meteor detection and non-periodic bursty interference removal of Arecibo Observatory data are presented in this paper. The statistical characteristics of the meteor signal and the interference signal are different. We utilize those properties to distinguish the signals. We calculate the central moments and apply a nonlinear filter to the power profile of received signals to detect and blank the interference signals. For meteor detection, we use a sliding window fast Fourier transform (FFT) which contains several inter-pulse period (IPP) signals. Experimental results demonstrate that the method efficiently and accurately removes the interference and detects the meteor.
BibTeX:
@article{Wen2005275,
  author = {C.-H. Wen and J.F. Doherty and J.D. Mathews and D. Janches},
  title = {Meteor detection and non-periodic bursty interference removal for Arecibo data },
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2005},
  volume = {67},
  number = {3},
  pages = {275 - 281},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682604002470},
  doi = {10.1016/j.jastp.2004.10.004}
}
Wen CH, Doherty JF and Mathews J (2005), "Adaptive filtering for the separation of incoherent scatter and meteor signals for Arecibo observation data", Journal of Atmospheric and Solar-Terrestrial Physics. Vol. 67(13), pp. 1190-1195.
BibTeX:
@article{Wen2005a,
  author = {Wen, C H and Doherty, J F and Mathews, J},
  title = {Adaptive filtering for the separation of incoherent scatter and meteor signals for Arecibo observation data},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
  year = {2005},
  volume = {67},
  number = {13},
  pages = {1190-1195},
  doi = {10.1016/j.jastp.2005.06.004}
}
Zhang S-R, Holt JM, van Eyken AP, McCready M, Amory-Mazaudier C, Fukao S and Sulzer M (2005), "Ionospheric local model and climatology from long-term databases of multiple incoherent scatter radars", Geophysical Research Letters. Vol. 32(20), pp. n/a-n/a.
BibTeX:
@article{Zhang2005,
  author = {Zhang, Shun-Rong and Holt, John M. and van Eyken, Anthony P. and McCready, Mary and Amory-Mazaudier, Christine and Fukao, Shoichiro and Sulzer, Michael},
  title = {Ionospheric local model and climatology from long-term databases of multiple incoherent scatter radars},
  journal = {Geophysical Research Letters},
  year = {2005},
  volume = {32},
  number = {20},
  pages = {n/a-n/a},
  doi = {10.1029/2005GL023603}
}
Zhou QH and Morton YT (2005), "Incoherent scatter radar study of photochemistry in the E-region", Geophysical Research Letters. Vol. 32(1), pp. n/a-n/a.
BibTeX:
@article{Zhou2005,
  author = {Zhou, Qihou H. and Morton, Yu T.},
  title = {Incoherent scatter radar study of photochemistry in the E-region},
  journal = {Geophysical Research Letters},
  year = {2005},
  volume = {32},
  number = {1},
  pages = {n/a-n/a},
  doi = {10.1029/2004GL021275}
}
Zhou Q, Friedman J, Raizada S, Tepley C and Morton YT (2005), "Morphology of nighttime ion, potassium and sodium layers in the meteor zone above Arecibo ", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 67(13), pp. 1245 - 1257.
Abstract: We use over ten years’ incoherent scatter radar (ISR) data and several years of potassium and sodium resonance lidar data to study the morphologies of ion, potassium, and sodium layering activities in the mesopause region above Arecibo, Puerto Rico. A tidal effect is clearly seen in the layer trajectories of all three species. Semidiurnal ion layer tidal structure is observed in the spring, summer, and fall at above 105 km altitude. Below 100 km altitude, the most consistent ion layers occur at 95 km altitude at 1800 local time (LT) during most time of the year except in the summer. The strongest ion layers occur around sunset hours at 106 km altitude in the summer. Although both potassium and sodium are alkaline metals, their layers exhibit very different characteristics. Throughout the mesopause region, sodium layer trajectories are always downward throughout the year, in response to the diurnal tide in this region. The tidal effect on the potassium layers can be seen mostly in the 90–95 km altitude region. While the mesopause height does not appear to be related to the seasonal variations of the potassium layers centroid height, it does appear to have great influence on that of the sodium layers. The potassium layer abundance is highest in the summer and a secondary peak occurs in the winter. The semiannual variation of the potassium layer abundance may provide an important clue to a better understanding of the potassium chemistry.
BibTeX:
@article{Zhou20051245,
  author = {Qihou Zhou and Jonathan Friedman and Shikha Raizada and Craig Tepley and Yu T. Morton},
  title = {Morphology of nighttime ion, potassium and sodium layers in the meteor zone above Arecibo },
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2005},
  volume = {67},
  number = {13},
  pages = {1245 - 1257},
  note = {Meteors and the MesopauseMeteors and the Mesopause },
  url = {http://www.sciencedirect.com/science/article/pii/S1364682605001161},
  doi = {10.1016/j.jastp.2005.06.013}
}
Bernhardt PA and Sulzer MP (2004), "Incoherent scatter measurements of ring-ion beam distributions produced by space shuttle exhaust injections into the ionosphere", Journal of Geophysical Research: Space Physics. Vol. 109(A2), pp. n/a-n/a.
Abstract: When the space shuttle Orbiting Maneuver Subsystem (OMS) engines burn in the ionosphere, two types of effects are produced. First, charge exchange between the exhaust molecules and the ambient O+-ions yields beams of high-speed molecular ions that can excite plasma turbulence. Second, the molecular ions eventually recombine with electrons to yield a plasma hole. The ion-beam interactions and the formation of artificial plasma holes in the ionosphere have been studied with ground-based, incoherent-scatter radars (ISRs) during the Shuttle Ionospheric Modification with Pulsed Localized Exhaust (SIMPLEX) series of experiments. The SIMPLEX II experiment took place in late July 1999 during the STS-93 flight of the Space Shuttle Columbia. The Orbital Maneuver Subsystem (OMS) engines provided controlled ion injections over the incoherent scatter radar (ISR) facilities located at Arecibo, Puerto Rico to excite unusual radar signatures. After charge exchange between the exhaust and the ambient plasma, pickup ions were produced with velocities near 10 km/s using a ram-burn orientation of the OMS engines relative to the vehicle orbit vector. During the SIMPLEX II experiment, the ISR spectra of the exhaust-modified plasma were obtained for the first time. The formation of ring-ion beam distributions was determined from curve fitting to the radar spectra. These spectra show the presence of the nonthermal ion distributions and enhanced scatter from electrons for thermal ion distributions with elevated ion temperatures. Analysis of the ion distributions in the modified ionosphere indicates that they were unstable and may have quickly generated plasma waves that along with ion-neutral collisions changed the ion-velocity distributions. The observations show that the perpendicular ion speed was rapidly reduced from 10 km/s to about 1 km/s. These observations open up the possibility of conducting a new series of experiments studying ring-ion beam instabilities that occur naturally in the auroral-region ionosphere and artificially in the space shuttle exhaust where there is large relative motion between the ion and neutral species.
BibTeX:
@article{Bernhardt2004,
  author = {Bernhardt, P. A. and Sulzer, M. P.},
  title = {Incoherent scatter measurements of ring-ion beam distributions produced by space shuttle exhaust injections into the ionosphere},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2004},
  volume = {109},
  number = {A2},
  pages = {n/a-n/a},
  doi = {10.1029/2002JA009693}
}
Clemesha BR, Batista PP, Simonich DM and Batista IS (2004), "Sporadic structures in the atmospheric sodium layer", Journal of Geophysical Research: Atmospheres. Vol. 109(D11), pp. n/a-n/a.
Abstract: The sporadic occurrence of layers of enhanced concentration of meteoric metals in the vicinity of the mesopause has been observed by lidar at many locations. These layers are much thinner than the background layer, last between a few minutes and many hours, and appear to be related to ionospheric sporadic E. A much more rare type of transient layer has been reported in the literature only once, by Kane et al. [2001]. The layers in question, observed in sodium by a lidar operating at Arecibo (18.3°N, 66.7°W), appear as C-shaped structures in the lidar height/time display. The structures, which have been observed at around 100 km, with durations around 30 min, appear not to be related to normal sporadic metals layers, and the Arecibo workers suggest that they might be produced by wave-breaking or Kelvin-Helmholtz billows. At São José dos Campos (23°S, 46°W) we observe C-structures in the sodium layer only very occasionally, but an analysis of their formation, together with simultaneous meteor winds measurements, suggests that the observed structures might be the result of wind-shear distortion of preexisting clouds of enhanced sodium concentration.
BibTeX:
@article{Clemesha2004,
  author = {Clemesha, Barclay R. and Batista, Paulo P. and Simonich, Dale M. and Batista, Inez S.},
  title = {Sporadic structures in the atmospheric sodium layer},
  journal = {Journal of Geophysical Research: Atmospheres},
  year = {2004},
  volume = {109},
  number = {D11},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2003JD004496},
  doi = {10.1029/2003JD004496}
}
Djuth FT, Sulzer MP, Gonzalez SA, Mathews JD, Elder JH and Walterscheid RL (2004), "A continuum of gravity waves in the Arecibo thermosphere?", Geophysical Research Letters. Vol. 31(16), pp. n/a-n/a.
Abstract: Previous incoherent radar studies at Arecibo Observatory, Puerto Rico have demonstrated that ~1–3% electron density “imprints” of internal gravity waves are routinely present in the Arecibo thermosphere (?118–500 km). A special radar technique involving photoelectron-enhanced plasma waves (PEPWs) was used for these observations. Recently, it was discovered that the trails of the gravity waves can be detected in standard incoherent scatter power profiles when properly filtered. This result was validated using simultaneous PEPW observations. This new development opens up the possibility of monitoring thermospheric gravity waves day and night. Preliminary studies indicate that gravity waves are continually propagating through the Arecibo thermosphere, and that “sets” of waves separated by approximately 20–60 min are typically present. With the aid of additional radar tests, it may be possible to unlock Arecibo power profiles recorded over the past 30 years for gravity wave studies. The precise origin of the waves is currently unknown.
BibTeX:
@article{Djuth2004,
  author = {Djuth, F. T. and Sulzer, M. P. and Gonzalez, S. A. and Mathews, J. D. and Elder, J. H. and Walterscheid, R. L.},
  title = {A continuum of gravity waves in the Arecibo thermosphere?},
  journal = {Geophysical Research Letters},
  year = {2004},
  volume = {31},
  number = {16},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2003GL019376},
  doi = {10.1029/2003GL019376}
}
Gonzalez SA, Sulzer MP, Nicolls MJ and Kerr RB (2004), "Solar cycle variability of nighttime topside helium ion concentrations over Arecibo", Journal of Geophysical Research: Space Physics. Vol. 109(A7), pp. n/a-n/a.
Abstract: The incoherent scatter radar mode and data extraction method used in topside experiments at the Arecibo Observatory are discussed. Helium ion concentrations in the lower topside ionosphere over Arecibo are presented for low and high solar flux periods of the same season (October). Data from 8-9 October 1988, 21-22 October 1995, 26-27 October 1997, and 12-13 October 2001 are compared. The data from October 1988 and 2001 are representative of high solar flux conditions, while the other two periods (1995 and 1997) are from low solar flux conditions. All data sets represent geomagnetic quiet periods over Arecibo and serve as examples of typical equinox topside conditions. For solar minimum the altitude distribution of the helium ions usually has a maximum near the O+ to H+ transition altitude (ht) during the night, usually around 550-650 km. The He+ number densities tend to be quite low, 2 or 3 × 103 cm-3 or <15% of the topside plasma density at the peak of the layer. For the higher solar flux case, however, He+ forms a more distinct layer at an altitude that is slightly above at night. The O+-to-He+ transition altitude (ht) is reported to be below after the postsunset collapse in these solar-maximum conditions, meaning that He+ is the dominant species. We find that the relative abundance of He+ can reach 60-65% of the topside plasma at the peak of this layer during these equinox conditions or up to 4 × 104 cm-3, with as low as 700 km and the He+ to H+ transition (ht) extending over 1000 km at night.
BibTeX:
@article{Gonzalez2004,
  author = {Gonzalez, Sixto A. and Sulzer, Michael P. and Nicolls, Michael J. and Kerr, Robert B.},
  title = {Solar cycle variability of nighttime topside helium ion concentrations over Arecibo},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2004},
  volume = {109},
  number = {A7},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2003JA010100},
  doi = {10.1029/2003JA010100}
}
Nicolls MJ, Kelley MC, Coster AJ, González SA and Makela JJ (2004), "Imaging the structure of a large-scale TID using ISR and TEC data", Geophysical Research Letters. Vol. 31(9), pp. n/a-n/a.
Abstract: Here we present North American observations of the 3-dimensional structure of large-scale traveling ionospheric disturbances (TIDs) that affected the low- and mid-latitude ionosphere during the stormtime period of October 1–2, 2002. Using TEC data from the American network of dual-frequency GPS receivers, we are able to examine the effect of the TIDs on the background TEC and thus image their horizontal scales. Incoherent scatter radar data from the Arecibo Observatory give information on the vertical structure of the disturbances. The meridional and zonal structure of the TIDs are explored by computing the TEC perturbation, a method which has a resolution of a fraction of a TEC unit. The technique is effective in mapping the global structure of large-scale disturbances, as the lower latitude perturbations can be examined at the same time as the higher latitude sources. The method may prove valuable in studying the formation and propagation of TIDs.
BibTeX:
@article{GRL:GRL18232,
  author = {Nicolls, Michael J. and Kelley, Michael C. and Coster, Anthea J. and González, Sixto A. and Makela, Jonathan J.},
  title = {Imaging the structure of a large-scale TID using ISR and TEC data},
  journal = {Geophysical Research Letters},
  year = {2004},
  volume = {31},
  number = {9},
  pages = {n/a--n/a},
  url = {http://dx.doi.org/10.1029/2004GL019797},
  doi = {10.1029/2004GL019797}
}
Hines CO, Childress LI, Kinney JB and Sulzer MP (2004), "Modeling of gravity-wave tail spectra in the middle atmosphere via numerical and Doppler-spread methods ", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 66(11), pp. 933 - 948.
Abstract: Wind fluctuations in the middle atmosphere exhibit an Eulerian spectral tail approximating to the form m?3 at large vertical wavenumbers m. The tail is taken here to result from a characteristically Eulerian nonlinearity in the governing fluid dynamic equations, a nonlinearity that is absent from a Lagrangian description. It is modeled here via a previously described analytic transformation from assumed model Lagrangian input spectra. The present work gives numerical expression to the earlier analytic results for the intensity of the tail. The resultant tail spectra are found to represent well the relevant data at reasonable values of Richardson number. Under an assumption of constant Richardson number, they exhibit saturation as height increases, as do the observations. Previously obtained approximate results, including those of the Doppler-spread theory of saturation, are found to represent well the new numerical results. Implications for that theory and for the associated Doppler-spread parameterization are discussed in a companion paper.
BibTeX:
@article{Hines2004933,
  author = {Colin O Hines and Lilian I Childress and Justin B Kinney and Michael P Sulzer},
  title = {Modeling of gravity-wave tail spectra in the middle atmosphere via numerical and Doppler-spread methods },
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2004},
  volume = {66},
  number = {11},
  pages = {933 - 948},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682604000707},
  doi = {10.1016/j.jastp.2004.02.004}
}
Hysell DL, Larsen MF and Zhou QH (2004), "Common volume coherent and incoherent scatter radar observations of mid-latitude sporadic E-layers and QP echoes", Annales Geophysicae. Vol. 22(9), pp. 3277-3290.
BibTeX:
@article{Hysell2004,
  author = {Hysell, D. L. and Larsen, M. F. and Zhou, Q. H.},
  title = {Common volume coherent and incoherent scatter radar observations of mid-latitude sporadic E-layers and QP echoes},
  journal = {Annales Geophysicae},
  year = {2004},
  volume = {22},
  number = {9},
  pages = {3277-3290},
  doi = {10.5194/angeo-22-3277-2004}
}
Janches D, Nolan MC and Sulzer M (2004), "Radiant measurement accuracy of micrometeors detected by the Arecibo 430 MHz Dual-Beam Radar", Atmospheric Chemistry and Physics. Vol. 4(3), pp. 621-626.
BibTeX:
@article{Janches2004,
  author = {Janches, D. and Nolan, M. C. and Sulzer, M.},
  title = {Radiant measurement accuracy of micrometeors detected by the Arecibo 430 MHz Dual-Beam Radar},
  journal = {Atmospheric Chemistry and Physics},
  year = {2004},
  volume = {4},
  number = {3},
  pages = {621-626},
  doi = {10.5194/acp-4-621-2004}
}
Kafando P and Petitdidier M (2004), "An attempt to calibrate the UHF strato-tropospheric radar at Arecibo using NexRad radar and disdrometer data", Annales Geophysicae. Vol. 22(12), pp. 4025-4034.
Abstract: The goal of this paper is to present a methodology to calibrate the reflectivity of the UHF Strato-Tropospheric (ST) radar located at NAIC in Puerto Rico. The UHF lower relevant altitude is at 5.9km, the melting layer being at around 4.8km. The data used for the calibration came from the observations of clouds, carried out with Strato-Tropospheric dual-wavelength (UHF and VHF) radars and a disdrometer; those instruments being located on the NAIC site in Arecibo, Puerto Rico. The National Weather Service operates other instruments like the radiosondes and the NexRad Radar in other sites.

The proposed method proceeds in two steps. The first consists of the comparison between the NexRad reflectivity and the reflectivity computed from the drop size distributions measured by the disdrometer for one day with a noticeable rainfall rate. In spite of the distance of both instruments, the agreement between the reflectivities of both instruments is enough good to be used as a reference for the UHF ST radar. The errors relative at each data set is found to be 2.75dB for the disdrometer and 4dB for the NexRad radar, following the approach of Hocking et al. (2001). The inadequacy between the two sampled volume is an important contribution in the errors.

The second step consists of the comparison between the NexRad radar reflectivity and the UHF non-calibrated reflectivity at the 4 altitudes of common observations during one event on 15 October 1998. Similar features are observed and a coefficient is deduced. An offset around 4.7dB is observed and the correlation factor lies between 0.628 and 0.730. According to the errors of the data sets, the precision on the calibration is of the order of 2dB. This method works only when there are precipitation hydrometeors above the NAIC site. However, the result of the calibration could be applied to other data obtained during the campaign, the only constraint being the same value of the transmitter power.

BibTeX:
@article{Kafando2004a,
  author = {Kafando, P. and Petitdidier, M.},
  title = {An attempt to calibrate the UHF strato-tropospheric radar at Arecibo using NexRad radar and disdrometer data},
  journal = {Annales Geophysicae},
  year = {2004},
  volume = {22},
  number = {12},
  pages = {4025-4034},
  url = {www.ann-geophys.net/22/4025/2004/},
  doi = {10.5194/angeo-22-4025-2004}
}
Kelley MC, Swartz WE and Makela JJ (2004), "Mid-latitude ionospheric fluctuation spectra due to secondary instabilities", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 66(17), pp. 1559 - 1565.
Abstract: The most spectacular night of mid-latitude spread F ever recorded at Arecibo is analyzed and compared with barium cloud observations made in the 1970s and with equatorial spread F. Strong evidence is found for a secondary instability driven either by a poleward electric field and a westward density gradient (both presumably due to a primary Perkins instability), or by a zero-order eastward wind flowing across the westward gradient. Spectra computed from the incoherent scatter density profiles of this event are very similar to the spectra of both barium striations and equatorial spread F. Estimates of the strength of the radar wave scattering expected from the fluctuation spectra are in good agreement with the VHF observations from that night. Finally, a poleward-surging, mid-latitude plasma bubble is seen to bifurcate in a manner similar to equatorial spread-F simulations.
BibTeX:
@article{Kelley2004,
  author = {Michael C. Kelley and Wesley E. Swartz and Jonathan J. Makela},
  title = {Mid-latitude ionospheric fluctuation spectra due to secondary instabilities},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2004},
  volume = {66},
  number = {17},
  pages = {1559 - 1565},
  note = {40 Years of Equatorial Aeronomy Sparked by the Jicamarca Radio Observatory },
  url = {http://www.sciencedirect.com/science/article/pii/S1364682604001610},
  doi = {10.1016/j.jastp.2004.07.004}
}
Kuo SP (2004), "On the cascade spectrum of Langmuir waves observed in Arecibo heating experiments", Physica Scripta. Vol. 69(2), pp. 115-119.
Abstract: Two parametric instabilities cascading Langmuir waves, which are the sideband of the parametric decay instability (PDI) excited by an O-mode HF heating wave, are studied. The first one decays a Langmuir pump wave into a Langmuir sideband and an ion acoustic wave. Both resonant and nonresonant cascade processes are considered. A nonresonant cascade of Langmuir waves proceeds at the same location and is severely hampered by the frequency mismatch effect. Resonant cascade takes place in different resonant locations to minimize the frequency mismatch effect, but it has to overcome the propagation loss of the mother Langmuir wave in each cascade step. Depending on the propagation loss, the resonant cascade could have a lower threshold, but cascade lines spread over a height region. The second one is a three-dimensional coupling process that employs the lower hybrid wave as the decay mode. Through this process, the nonresonant cascade of Langmuir waves produces a broad spectrum of frequency-downshifted plasma waves, similar to that of experimentally observed HFPLs, in a narrow altitude range, which is preferentially located near the matching height of the PDI sideband.
BibTeX:
@article{Kuo_2004,
  author = {Kuo, S. P.},
  title = {On the cascade spectrum of Langmuir waves observed in Arecibo heating experiments},
  journal = {Physica Scripta},
  year = {2004},
  volume = {69},
  number = {2},
  pages = {115-119},
  url = {http://iopscience.iop.org/1402-4896/69/2/007},
  doi = {10.1238/Physica.Regular.069a00115}
}
Larsen MF, Liu AZ, Gardner CS, Kelley MC, Collins S, Friedman J and Hecht JH (2004), "Observations of overturning in the upper mesosphere and lower thermosphere", Journal of Geophysical Research: Atmospheres. Vol. 109(D2), pp. n/a-n/a.
Abstract: A number of observations of the sodium density primarily in the mesosphere and lower thermosphere (but also of the electron density structure) have shown what appears to be overturning or convective roll cells near the transition from the mesosphere to the lower thermosphere. The cells are found in the region between 95 and 105 km and occur near the boundary between the region of lower stability in the mesosphere and the region of higher stability in the lower thermosphere. The vertical scale for the rolls is ~5–6 km, and the timescale is ~1–3 hours. The rolls occur in a region characterized by large shear in the neutral winds, but the timescales are too long to be explained by simple Kelvin-Helmholtz instability. We present observations from the University of Illinois lidar facility located at the Starfire Optical Range near Albuquerque, New Mexico, from the Arecibo Observatory in Puerto Rico, and from the Maui/MALT Lidar Facility located on Maui in Hawaii that show the overturning structure. possible mechanisms for generating the convective rolls are discussed, Including the relationship of the observed features to the characteristics expected for an inflection point instability.
BibTeX:
@article{Larsen2004,
  author = {Larsen, M. F. and Liu, A. Z. and Gardner, C. S. and Kelley, M. C. and Collins, S. and Friedman, J. and Hecht, J. H.},
  title = {Observations of overturning in the upper mesosphere and lower thermosphere},
  journal = {Journal of Geophysical Research: Atmospheres},
  year = {2004},
  volume = {109},
  number = {D2},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2002JD003067},
  doi = {10.1029/2002JD003067}
}
Lobzin VV and Pavlov AV (2004), "Relation of the Electron Temperature to the Concentrations of the Electrons and Neutral Components in the Daytime Ionosphere over Arecibo Station", International Journal of Geomagnetism and Aeronomy. Vol. 44(4), pp. 453-460.
BibTeX:
@article{Lobzin2004,
  author = {Lobzin, V. V. and Pavlov, A. V.},
  title = {Relation of the Electron Temperature to the Concentrations of the Electrons and Neutral Components in the Daytime Ionosphere over Arecibo Station},
  journal = {International Journal of Geomagnetism and Aeronomy},
  year = {2004},
  volume = {44},
  number = {4},
  pages = {453-460}
}
Love A (2004), "Arecibo Observatory 40th anniversary celebration", IEEE Antennas and Propagation Magazine. Vol. 46(1), pp. 94-97.
Abstract: The National Astronomy and Ionosphere Center (NAIC), operated by Cornell University for the National Science Foundation, has its laboratory at Arecibo in Puerto Rico. The observatory's main instrument is a radio/radar telescope that utilizes a giant reflector antenna 1,000 feet in diameter, the largest in the world by considerable margin. A 40th anniversary celebration of the 1963 inauguration of this observatory was held at the site in Puerto Rico on November 1, 2003. This paper discusses the development of the said antenna, its characteristics and the upgrading of the system. The paper includes a discussion of what transpired during the said anniversary celebration.
BibTeX:
@article{Love2004,
  author = {Love, A.W.},
  title = {Arecibo Observatory 40th anniversary celebration},
  journal = {IEEE Antennas and Propagation Magazine},
  year = {2004},
  volume = {46},
  number = {1},
  pages = {94-97},
  url = {http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=1296152},
  doi = {10.1109/MAP.2004.1296152}
}
Murad E and Roth C (2004), "Evaporation of high speed sporadic meteors", Atmospheric Chemistry and Physics. Vol. 4(3), pp. 737-740.
BibTeX:
@article{Murad2004,
  author = {Murad, E. and Roth, C.},
  title = {Evaporation of high speed sporadic meteors},
  journal = {Atmospheric Chemistry and Physics},
  year = {2004},
  volume = {4},
  number = {3},
  pages = {737-740},
  doi = {10.5194/acp-4-737-2004}
}
Pandey V, Sethi N and Mahajan K (2004), "Topside electron temperature models for low and high solar activity ", Advances in Space Research . Vol. 33(6), pp. 959-962.
BibTeX:
@article{Pandey2004,
  author = {V.K. Pandey and N.K. Sethi and K.K. Mahajan},
  title = {Topside electron temperature models for low and high solar activity },
  journal = {Advances in Space Research },
  year = {2004},
  volume = {33},
  number = {6},
  pages = {959-962},
  url = {http://www.sciencedirect.com/science/article/pii/S0273117703010238},
  doi = {10.1016/j.asr.2003.07.011}
}
Pavlov AV, Fukao S and Kawamura S (2004), "Comparison of the measured and modeled electron densities, and electron and ion temperatures in the low-latitude ionosphere during 19-21 March 1988", Annales Geophysicae. Vol. 22(8), pp. 2747-2763.
BibTeX:
@article{Pavlov2004,
  author = {Pavlov, A. V. and Fukao, S. and Kawamura, S.},
  title = {Comparison of the measured and modeled electron densities, and electron and ion temperatures in the low-latitude ionosphere during 19-21 March 1988},
  journal = {Annales Geophysicae},
  year = {2004},
  volume = {22},
  number = {8},
  pages = {2747-2763},
  doi = {10.5194/angeo-22-2747-2004}
}
Pavlov AV, Fukao S and Kawamura S (2004), "F-region ionospheric perturbations in the low-latitude ionosphere during the geomagnetic storm of 25-27 August 1987", Annales Geophysicae. Vol. 22(10), pp. 3479-3501.
BibTeX:
@article{Pavlov2004a,
  author = {Pavlov, A. V. and Fukao, S. and Kawamura, S.},
  title = {F-region ionospheric perturbations in the low-latitude ionosphere during the geomagnetic storm of 25-27 August 1987},
  journal = {Annales Geophysicae},
  year = {2004},
  volume = {22},
  number = {10},
  pages = {3479-3501},
  doi = {10.5194/angeo-22-3479-2004}
}
Raizada S, Tepley C, Janches D, Friedman J, Zhou Q and Mathews J (2004), "Lidar observations of Ca and K metallic layers from Arecibo and comparison with micrometeor sporadic activity ", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 66(6–9), pp. 595 - 606.
Abstract: We report on the first simultaneous observations of Ca and K metallic layers using the low-latitude lidar systems located at the Arecibo Observatory in Puerto Rico (18.35°N, 66.75°W). We often observe sudden increases in both Ca and K densities during early morning hours on nights where meteor showers take place. During these periods, the Ca/K abundance ratio varied between 2 and 3. On occasion, differences were observed in Ca and K layers, which relate to differences in the chemistry of the two metals. It is known that metallic layers display distinct seasonal variations, but chemistry alone cannot explain the measured differences. Thus, we examined whether or not the seasonal distribution of micrometeoroids, derived from meteor observations using the Arecibo 430 MHz radar, can account for the dissimilar metallic observations. We found that the deposition flux of micrometeoroids, with particle sizes ranging between 0.5 and 100 ?m, increased by a factor of two during the summer as compared with the winter, suggesting a seasonal variation of their sporadic activity. In addition, our data support the idea that differential ablation leads to a depletion of Ca atoms in the mesosphere.
BibTeX:
@article{Raizada2004595,
  author = {S. Raizada and C.A. Tepley and D. Janches and J.S. Friedman and Q. Zhou and J.D. Mathews},
  title = {Lidar observations of Ca and K metallic layers from Arecibo and comparison with micrometeor sporadic activity },
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2004},
  volume = {66},
  number = {6–9},
  pages = {595 - 606},
  note = {Dynamics and Chemistry of the MLT Region - PSMOS 2002 International Symposium },
  url = {http://www.sciencedirect.com/science/article/pii/S1364682604000239},
  doi = {10.1016/j.jastp.2004.01.030}
}
Rodrigues FS, Brum CGM, Makita K, Nishino M, Paula ERd, Abdu MA, Nozaki K, Contreira DB, Silva MRd and Schuch NJ (2004), "A commercial radio receiver for lower ionosphere monitoring: Initial results", Geofisica Internacional. Vol. 43, pp. 193-198.
Abstract: A commercial computer controlled radio receiver has been used to measure signal strength of High Frequency (HF) signals in order to study the effects of geophysical events on radio communications and to test the system for ionospheric monitoring. The system was installed at the Southern Space Observatory (OES/CRSPE/INPE) in São Martinho da Serra, Brazil (29.43S, 53.8W, B = 23350 nT). Initial results show that this system is able to detect ionospheric radio absorption events. The commercial radio receiver has a computer serial interface, to control the reception frequency in order to acquire the values of the received signal strength. We describe the system and some initial results on radio absorption events associated to C and M classes of x-ray solar flares. The results suggest the possibility of using this low-cost system to study the daily variation of the lower ionosphere ionization and to study events of ionospheric absorption. Long period measurements give statistical information about the magnitude and time scale of fading, that can be used for planning radio links.
BibTeX:
@article{Rodrigues2004,
  author = {Rodrigues, F S and Brum, C G M and Makita, K and Nishino, M and Paula, E R de and Abdu, M A and Nozaki, K and Contreira, D B and Silva, M R da and Schuch, N J},
  title = {A commercial radio receiver for lower ionosphere monitoring: Initial results},
  journal = {Geofisica Internacional},
  year = {2004},
  volume = {43},
  pages = {193-198},
  note = {Arecibo author},
  url = {http://www.geofisica.unam.mx/unid_apoyo/editorial/publicaciones/investigacion/geofisica_internacional/anteriores/2004/02/Rodrigues.pdf}
}
Rosado-Roman JM, Swartz WE and Farley DT (2004), "Plasma instabilities observed in the E region over Arecibo and a proposed nonlocal theory", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 66(17), pp. 1593-1602.
BibTeX:
@article{Rosado-Roman2004,
  author = {Jose M. Rosado-Roman and Wesley E. Swartz and Donald T. Farley},
  title = {Plasma instabilities observed in the E region over Arecibo and a proposed nonlocal theory},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2004},
  volume = {66},
  number = {17},
  pages = {1593-1602},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682604001622},
  doi = {10.1016/j.jastp.2004.07.005}
}
Sethi N, Pandey V and Mahajan K (2004), "Seasonal and solar activity changes of electron temperature in the F-region and topside ionosphere", Advances in Space Research. Vol. 33(6), pp. 970-974.
BibTeX:
@article{Sethi2004,
  author = {N.K Sethi and V.K Pandey and K.K Mahajan},
  title = {Seasonal and solar activity changes of electron temperature in the F-region and topside ionosphere},
  journal = {Advances in Space Research},
  year = {2004},
  volume = {33},
  number = {6},
  pages = {970-974},
  doi = {10.1016/j.asr.2003.08.008}
}
Sulzer MP (2004), "Meteoroid velocity distribution derived from head echo data collected at Arecibo during regular world day observations", Atmospheric Chemistry and Physics. Vol. 4(4), pp. 947-954.
BibTeX:
@article{Sulzer2004,
  author = {Sulzer, M. P.},
  title = {Meteoroid velocity distribution derived from head echo data collected at Arecibo during regular world day observations},
  journal = {Atmospheric Chemistry and Physics},
  year = {2004},
  volume = {4},
  number = {4},
  pages = {947-954},
  doi = {10.5194/acp-4-947-2004}
}
Urbina J, Kudeki E, Franke SJ and Zhou Q (2004), "Analysis of a mid-latitude E-region LQP event observed during the Coqui 2 Campaign", Geophysical Research Letters. Vol. 31(14), pp. n/a-n/a.
Abstract: Arecibo ISR observations and VHF coherent backscatter data collected with a radar situated in southern Puerto Rico are examined to understand the causes of quasi-periodic variations in VHF returns from lower E-region heights (~93 km). It is found that Bragg scale density irregularities causing the observed VHF backscatter are formed and propagated horizontally in a density perturbation field localized at the upper boundary of a tidal ion layer. The density perturbation has a 7 km horizontal wavelength, propagates in southwest direction, and it is not aligned with the geomagnetic field. Thus the production mechanism of the observed density perturbation cannot be the gradient-drift instability often invoked to account for the generation of mid-latitude sporadic E radar echoes. Nevertheless, secondary gradient-drift instability operating on the gradients of the southwest propagating perturbation remains the most likely cause of Bragg scale electron density waves responsible for the VHF returns.
BibTeX:
@article{Urbina2004,
  author = {Urbina, Julio and Kudeki, Erhan and Franke, Steven J. and Zhou, Qihou},
  title = {Analysis of a mid-latitude E-region LQP event observed during the Coqui 2 Campaign},
  journal = {Geophysical Research Letters},
  year = {2004},
  volume = {31},
  number = {14},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2004GL020031},
  doi = {10.1029/2004GL020031}
}
Wen CH, Doherty JF and Mathews JD (2004), "Time-frequency radar processing for meteor detection", IEEE Transactions on Geoscience and Remote Sensing. Vol. 42(3), pp. 501-510.
Abstract: In this paper, we present signal processing techniques to detect meteor returns from Arecibo Observatory 430-MHz UHF radar data. We exploit the characteristics of the transmit waveform in the frequency domain as well as in the time domain. Two detection methods are investigated. First, when a meteor is present in the radar return over several interpulse periods, there will be a periodic structure in frequency spectrum. By detecting this structure, we detect the presence of a meteor. Second, we construct a matched filter bank to detect the energy of different Doppler frequency components. When the energy exceeds a certain threshold, we declare meteor detection. We also find the altitude of a meteor by finding the peak of the matched filter output. Analytical and experimental results show that we can efficiently and reliably detect meteors using these methods.
BibTeX:
@article{Wen2004,
  author = {Wen, C H and Doherty, J F and Mathews, J D},
  title = {Time-frequency radar processing for meteor detection},
  journal = {IEEE Transactions on Geoscience and Remote Sensing},
  year = {2004},
  volume = {42},
  number = {3},
  pages = {501-510},
  doi = {10.1109/TGRS.2003.821344}
}
Zhang S, Thayer J, Roble R, Salah J, Shepherd G, Goncharenko L and Zhou Q (2004), "Latitudinal variations of neutral wind structures in the lower thermosphere for the March equinox period", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 66(1), pp. 105-117.
Abstract: Neutral winds in the lower thermosphere (95–130 km) measured during the March equinox period (1991–1992) by
ground-based incoherent scatter radars at Arecibo (18oN), Millstone Hill (42:5oN), and Sondrestrom (67oN) and by the
space-based wind imaging interferometer (WINDII) are compared and show overall good agreement but some differences.
At 18oN, the wind field in the altitude region of 95–110 km displays prevailing upward propagating diurnal tides with wavelengths
of about 22 km. The diurnal structure is afected by the semidiurnal tide resulting in regular minima separated by
11–12 h. At altitudes above 110 km, the diurnal tide dominant wind structure changes to the semidiurnal tide dominant structure
as illustrated clearly by WINDII data with 24 h coverage. Winds at 42:5oN and 67oN show similar structures in which
winds at 105–115 km are generally anti-sunward. Daytime ISR winds show prevailing upward propagating semidiurnal tides
with wavelengths of 35–70 km. Winds from WINDII reveal the existence of the in situ thermospheric diurnal tide with amplitudes
comparable to those of the semidiurnal tide. The superimposition of the two tides result in a wind field stronger during
daytime than during nighttime at mid- and high-latitudes. Geomagnetic infuence on neutral winds is negligible at low- and
mid-latitudes under solar quiet conditions, but is observed at high-latitudes, where wind vectors follow a clockwise one-cell
pattern at altitudes above about 118 km in geomagnetic coordinates. Most recent simulations for the three latitudes provided
by the NCAR thermosphere/ionosphere/mesosphere electrodynamics general circulation model are compared to the observations.
The results at low- and mid-latitudes agree well with the observed winds in both wind structures and magnitudes, and
reveal details of wave transition. Simulations for high-latitudes are less satisfactory, and require further improvements.
BibTeX:
@article{Zhang2004,
  author = {S.P. Zhang and J.P. Thayer and R.G. Roble and J.E. Salah and G.G. Shepherd and L.P. Goncharenko and Q.H. Zhou},
  title = {Latitudinal variations of neutral wind structures in the lower thermosphere for the March equinox period},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2004},
  volume = {66},
  number = {1},
  pages = {105-117},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682603002074},
  doi = {10.1016/j.jastp.2003.09.011}
}
Zhou QH, Morton YT, Mathews JD and Janches D (2004), "Aspect sensitivity of VHF echoes from field aligned irregularities in meteor trails and thin ionization layers", Atmospheric Chemistry and Physics. Vol. 4(3), pp. 685-692.
Abstract: The aspect sensitivity of VHF echoes from field aligned irregularities (FAI) within meteor trails and thin ionization layers is studied using numerical models. Although the maximum power is obtained when a radar is pointed perpendicular to the field line (pB), substantial power can be obtained off the pB direction if the ionization trail/layer is thin. When the FAI length along B is 20 m, the power observed 6° off pB is about 10 db below that perpendicular to the B direction. Meteoric FAI echoes can potentially be used to determine the diffusion rate in the mesopause region. Based on the aspect sensitivity analysis, we conclude that the range spread trail echoes far off pB observed by powerful VHF radars are likely due to overdense meteors. Our simulation also shows that ionospheric FAI echoes can have an altitude smearing effect of about 4 km if the vertical extension of a FAI-layer is around 100 m, which has often been observed at Arecibo. The altitude smearing effect can account for the fact that the Es-layers observed by the Arecibo incoherent scatter radar are typically much narrower than FAI-layers and the occurrence of double spectral peaks around the Es-layer altitude in FAI echoes.
BibTeX:
@article{Zhou2004,
  author = {Zhou, Q. H. and Morton, Y. T. and Mathews, J. D. and Janches, D.},
  title = {Aspect sensitivity of VHF echoes from field aligned irregularities in meteor trails and thin ionization layers},
  journal = {Atmospheric Chemistry and Physics},
  year = {2004},
  volume = {4},
  number = {3},
  pages = {685-692},
  doi = {10.5194/acp-4-685-2004}
}
Bernhardt PA, Gondarenko NA, Guzdar PN, Djuth FT, Tepley CA, Sulzer MP, Ossakow SL and Newman DL (2003), "Using radio-induced aurora to measure the horizontal structure of ion layers in the lower thermosphere", Journal of Geophysical Research: Space Physics. Vol. 108(A9), pp. n/a-n/a.
Abstract: Two-dimensional images of sporadic E layers have been produced using a technique called radio-induced aurora. This technique makes the ion layer regions glow when being stimulated by high-power radio waves. Normally, the neutral regions near the ion layers do not radiate visible emissions. Experiments in January 1998 at Arecibo Observatory in Puerto Rico have shown that the ion layer regions at 120 km altitude can be made to glow at 557.7 nm and other wavelengths by illuminating them with radio waves at 3.175 MHz with effective radiated powers of 80 MW. The regions of the sporadic E layers that have electron densities greater than the critical density for reflection of the radio waves emit energetic electrons that collide with and excite atmospheric atomic oxygen and molecular nitrogen. Because the electron collisions increase at lower altitudes where the neutral densities are higher, major differences in excitation can occur between layers at 120 km altitude and at 100 km altitude. A charge-coupled device imager located on the ground is used to capture images of the glowing E region structures. The camera exposure times were in the range of 15–45 s. The images obtained using this technique show a wide variety of structures in the sporadic E layers. Some layers cover the 15 × 30 km region illuminated by the radio wave beam. Other layers show strong modulation of the E region by instabilities driven by a shear in the neutral wind. Two-dimensional computer simulations of the coupling between neutral wind turbulence and the ion layers replicate the structure shown in the images. The optical emissions are explained using one- and two-dimensional simulations of radio propagation to produce localized regions of large electric fields. Electrons are accelerated out of these regions yielding the artificial aurora.
BibTeX:
@article{Bernhardt2003,
  author = {Bernhardt, P. A. and Gondarenko, N. A. and Guzdar, P. N. and Djuth, F. T. and Tepley, C. A. and Sulzer, M. P. and Ossakow, S. L. and Newman, D. L.},
  title = {Using radio-induced aurora to measure the horizontal structure of ion layers in the lower thermosphere},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2003},
  volume = {108},
  number = {A9},
  pages = {n/a-n/a},
  doi = {10.1029/2002JA009712}
}
Bishop RL and Earle GD (2003), "Metallic ion transport associated with midlatitude intermediate layer development", Journal of Geophysical Research: Space Physics. Vol. 108(A1), pp. SIA 3-1/SIA 3-8.
Abstract: Although intermediate layers are frequently observed by the Arecibo Incoherent Radar Observatory and by ionosondes around the world, many questions still remain regarding their formation, structure, and composition. In this paper, we explore the effect of metallic ions, specifically Fe+, on intermediate layer development and evolution. Several studies have demonstrated that layers can form from either molecular or metallic ions. This paper extends these earlier studies by quantifying the effect of metallic ions on intermediate layer morphology. We show that the efficiency of metallic ion transport depends significantly on the amplitude and wavelength of the imposed horizontal wind field. Specifically, larger amplitudes and longer wavelengths result in increased ion transport in the direction of the propagating neutral wind field.
BibTeX:
@article{Bishop2003,
  author = {Bishop, R. L. and Earle, G. D.},
  title = {Metallic ion transport associated with midlatitude intermediate layer development},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2003},
  volume = {108},
  number = {A1},
  pages = {SIA 3-1/SIA 3-8},
  doi = {10.1029/2002JA009411}
}
Boyer E, Larzabal P, Adnet C and Petitdidier M (2003), "Parametric spectral moments estimation for wind profiling radar", IEEE Transactions on Geoscience and Remote Sensing. Vol. 41(8), pp. 1859-1868.
Abstract: The purpose of this work is the estimation of Doppler echoes spectral moments. In case of strong overlapping, Fourier-like techniques provide poor results because of the lack of resolution. We propose the use of stochastic maximum-likelihood (SML) and subspace-based methods (WPSF algorithm) for a joint estimation of spectral moments. The statistical performances (theoretical and empirical by Monte Carlo simulations) of estimators are compared with the Cramer-Rao lower bound. The results of tests performed on very high frequency (VHF) times series obtained during Thunderstorm, Arecibo, PR during September and October 1998 validate the model and algorithms and confirm the interest of both approaches.
BibTeX:
@article{Boyer2003,
  author = {Boyer, E. and Larzabal, P. and Adnet, C. and Petitdidier, M.},
  title = {Parametric spectral moments estimation for wind profiling radar},
  journal = {IEEE Transactions on Geoscience and Remote Sensing},
  year = {2003},
  volume = {41},
  number = {8},
  pages = {1859-1868},
  doi = {10.1109/TGRS.2003.813487}
}
Friedman JS, Tepley CA, Raizada S, Zhou QH, Hedin J and Delgado R (2003), "Potassium Doppler-resonance lidar for the study of the mesosphere and lower thermosphere at the Arecibo Observatory", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 65(16-18), pp. 1411-1424.
Abstract: We have developed a lidar to study the temperature structure of the nighttime mesopause region over the Arecibo Observatory (18.35°N, 66.75°W) by measuring the lineshape of the fluorescence spectrum of atomic potassium that is deposited in the mesosphere and lower thermosphere (MLT) by meteors. To demonstrate how the potassium lidar can enhance MLT studies at Arecibo, we show recent results for: (1) comparisons with airglow temperature measurements; (2) simultaneous operations with stratospheric and mesospheric temperature profiling by Rayleigh lidar; (3) simultaneous observations of K, Ca+, and E-region electron density profiles; and (4) occurrences of sporadic K layers, and relationships to sporadic E layers.
BibTeX:
@article{Friedman2003,
  author = {Jonathan S. Friedman and Craig A. Tepley and Shikha Raizada and Qihou H. Zhou and Jonas Hedin and Rubén Delgado},
  title = {Potassium Doppler-resonance lidar for the study of the mesosphere and lower thermosphere at the Arecibo Observatory},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2003},
  volume = {65},
  number = {16-18},
  pages = {1411-1424},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682603002050},
  doi = {10.1016/j.jastp.2003.09.004}
}
Friedman JS (2003), "Tropical mesopause climatology over the Arecibo Observatory", Geophysical Research Letters. Vol. 30(12), pp. n/a-n/a.
Abstract: We report on the first annual cycle of mesopause-region (82–105 km) temperature profiles at a tropical latitude site, the Arecibo Observatory (18.35°N, 66.75°W), measured by potassium resonance lidar. Based on 74 night-time temperature profiles of observing periods greater than 5 hours we observe a mean temperature profile with a mesopause altitude of 98 km and temperature of 193 K. The annual mean nighttime temperature profile is similar to that seen at mid-latitudes, but there are striking differences in seasonal structure. The mesopause region mean seasonal structure at Arecibo experiences a temperature minimum of 176 K at 100 km during mid-summer. The winter period minimum of about 190 K is found mostly in a broad flat distribution between 90 and 95 km, and less frequently near 100 km.
BibTeX:
@article{Friedman2003a,
  author = {Friedman, Jonathan S.},
  title = {Tropical mesopause climatology over the Arecibo Observatory},
  journal = {Geophysical Research Letters},
  year = {2003},
  volume = {30},
  number = {12},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2003GL016966},
  doi = {10.1029/2003GL016966}
}
Gelinas LJ, Kelley MC, Sulzer MP, Mishin E and Starks MJ (2003), "In situ observations during an HF heating experiment at Arecibo: Evidence for Z-mode and electron cyclotron harmonic effects", Journal of Geophysical Research: Space Physics. Vol. 108(A10), pp. n/a-n/a.
Abstract: On 11 March 1998 the Langmuir Turbulence sounding rocket was launched through the Arecibo heater beam during an experiment to measure electric fields and plasma densities in the heater interaction region. In spite of a serious degradation of the Arecibo heater, the rocket data has provided evidence of Z mode waves and field aligned striations above the O mode reflection height. These observations give credence to the theory that Z mode wave interactions with field-aligned striations may be, in part, responsible for some of the features of the reflected HF spectrum observed in heating experiments. We also find strong low-frequency electric fields where the local plasma frequency matches an electron cyclotron harmonic. This suggests that electron Bernstein modes must be generated in the interaction process and can propagate to regions where they are severely damped.
BibTeX:
@article{Gelinas2003,
  author = {Gelinas, L. J. and Kelley, M. C. and Sulzer, M. P. and Mishin, E. and Starks, M. J.},
  title = {In situ observations during an HF heating experiment at Arecibo: Evidence for Z-mode and electron cyclotron harmonic effects},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2003},
  volume = {108},
  number = {A10},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2003JA009922},
  doi = {10.1029/2003JA009922}
}
Lee C-C, Liu J-Y, Pan C-J and Hsu H-H (2003), "The intermediate layers and associated tidal motions observed by a digisonde in the equatorial anomaly region", Annales Geophysicae. Vol. 21(4), pp. 1039-1045.
BibTeX:
@article{Lee2003,
  author = {Lee, C.-C. and Liu, J.-Y. and Pan, C.-J. and Hsu, H.-H.},
  title = {The intermediate layers and associated tidal motions observed by a digisonde in the equatorial anomaly region},
  journal = {Annales Geophysicae},
  year = {2003},
  volume = {21},
  number = {4},
  pages = {1039-1045},
  doi = {10.5194/angeo-21-1039-2003}
}
Lyons WA, CCM, Nelson TE, Armstrong RA, Pasko VP and Stanley MA (2003), "Upward Electrical Discharges From Thunderstorm Tops", Bulletin of the American Meteorological Society. Vol. 84, pp. 445-454.
Abstract: A variety of storm top electrical discharges have been observed using several types of low-light imagers, film, and the human eye. Recently, a video recorded an unprecedented, bright blue upward discharge from a tropical thunderstorm top near Puerto Rico. The event reached the base of the ionosphere. The horizontal dimensions of cloud top discharges can range from 100 m to several kilometers. Upward extents vary from 100 m to 70 km. Shapes include “points” of light, upwardly flaring trumpets, and narrow, vertical, lightning-like channels, some topped with expanding blue, flame-like features. Visual appearances range from brilliant white lightning-like channels to a grainy, almost particulate appearing jets of dim blue light, and sometimes as a blue flame within which a brilliant white channel appears. The classical blue jet is at the lower limit of human night vision whereas some upward discharges have been clearly seen during daylight. Cloud top “pixies” last no longer than 16.7 ms, whereas upward lightning-like channels are often characterized as long lasting (2.0 s or more). To date, optical measurements have not associated cloudtop events with specific lightning flashes. There is a strong tendency for all such events to occur above the convective dome of rapidly intensifying thunderstorms. It is possible that the great diversity of forms illustrates the complexity inherent in the upward streamer mechanism for blue jets. It is also possible that the basic blue jet is only one of several distinct classes of discharges from highly electrified storm cloud tops. Future research should focus on rapidly growing convective storm tops, including supercells and intense oceanic storms, as opposed to the stratiform regions of large mesoscale convective systems that have characterized sprite observations to date.
BibTeX:
@article{Lyons2003,
  author = {Walter A. Lyons and CCM and Thomas E. Nelson and Russell A. Armstrong and Victor P. Pasko and Mark A. Stanley},
  title = {Upward Electrical Discharges From Thunderstorm Tops},
  journal = {Bulletin of the American Meteorological Society},
  year = {2003},
  volume = {84},
  pages = {445-454},
  url = {http://dx.doi.org/10.1175/BAMS-84-4-445}
}
Makela JJ, Kelley MC, Gonzalez SA, Aponte N and Sojka JJ (2003), "Mid-latitude plasma and electric field measurements during space weather month, September 1999", Journal of Atmospheric and Solar-Terrestrial Physics. Vol. 65, pp. 1077-1085.
Abstract: Using data collected during the September 1999 combined ionospheric campaign (CIC), we examine the effects of moderate geomagnetic activity on low and mid-latitudes. Perturbations in the zonal electric field, measured at both Jicamarca and Arecibo, are the most striking aspect of this data. These eastward electric fields resulted in a poleward advection of the Appleton anomaly to mid-latitudes, where it was observed as a gradient in the nighttime electron density, as measured by the Arecibo incoherent scatter radar. This gradient was severe enough that it was observable in airglow measurements at 630.0 and 777.4nm. To put this data into context, we also examine the worldwide conditions during this time period and find evidence for several substorms, penetrating electric fields, and disturbance dynamo electric fields.
BibTeX:
@article{Makela2003,
  author = {Makela, J. J. and Kelley, M. C. and Gonzalez, S. A. and Aponte, N. and Sojka, J. J.},
  title = {Mid-latitude plasma and electric field measurements during space weather month, September 1999},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
  year = {2003},
  volume = {65},
  pages = {1077-1085},
  url = {http://dx.doi.org/10.1016/j.jastp.2003.07.002},
  doi = {10.1016/j.jastp.2003.07.002}
}
Mathews J, Doherty J, Wen C-H, Briczinski S, Janches D and Meisel D (2003), "An update on UHF radar meteor observations and associated signal processing techniques at Arecibo Observatory ", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 65(10), pp. 1139 - 1149.
Abstract: Over the past 8 years UHF radar meteor observations made at Arecibo Observatory (Puerto Rico) have evolved significantly while several long-standing meteor science issues have been solved and new ones raised. We start with a review of the current signal processing approach that includes significant new techniques with respect to identification of a meteor event and the eventual extraction of physical parameters. We then consider some basic radio science issues surrounding these observations. Current Doppler observations—now available with Doppler resolutions of &lt;10 m/s for meteor speeds ranging to nearly 100 km/s—have underscored issues related to the speed-distribution of at least micrometeoroids. Radar scattering mechanisms and the possibility of bias in the reported observations are considered. Additionally, we emphasize that the technique described here is almost entirely distinct from the classical trail-echo meteor radars.
BibTeX:
@article{Mathews20031139,
  author = {J.D. Mathews and J. Doherty and C.-H. Wen and S.J. Briczinski and D. Janches and D.D. Meisel},
  title = {An update on UHF radar meteor observations and associated signal processing techniques at Arecibo Observatory },
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2003},
  volume = {65},
  number = {10},
  pages = {1139 - 1149},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682603001767},
  doi = {10.1016/j.jastp.2003.07.009}
}
Pandey V, Sethi N and Mahajan K (2003), "Dependence of F2- peak height on solar activity: A study with incoherent scatter measurements", Advances in Space Research . Vol. 31(3), pp. 543-548.
Abstract: We have used about 16000 high resolution electron density profiles from Arecibo (18.4 N, 66.7 W, dip 50°) incoherent scatter radar for the years 1974–1977 and 1989–1990 to study the control of solar activity on the F2 peak height (hmF2). Although the general trend of diurnal variations in hmF2 are nearly identical (i.e. maximum around midnight and minimum around sunrise) during low as well as high solar activity, the median hmF2 increases by about 100 km from solar minimum to solar maximum. Further, there is a considerable day-to-day variability in hmF2. Comparison of measured hmF2 with the IRI (derived from numerical map of M(3000)F2) reveals that IRI generally overestimates this parameter during low solar activity and underestimates during high solar activity.
BibTeX:
@article{Pandey2003,
  author = {V.K. Pandey and N.K. Sethi and K.K. Mahajan},
  title = {Dependence of F2- peak height on solar activity: A study with incoherent scatter measurements},
  journal = {Advances in Space Research },
  year = {2003},
  volume = {31},
  number = {3},
  pages = {543-548},
  url = {http://www.sciencedirect.com/science/article/pii/S0273117703000498},
  doi = {10.1016/S0273-1177(03)00049-8}
}
Raizada S and Tepley CA (2003), "Seasonal variation of mesospheric iron layers at Arecibo: First results from low-latitudes", Geophysical Research Letters. Vol. 30(2), pp. n/a-n/a.
Abstract: We present the annual variation of the distribution of neutral iron of the low-latitude mesopause region measured at the Arecibo Observatory using resonance fluorescence lidar. A comparison was made between our low-latitude measurements and similar mid-and high-latitude observations of Fe column abundance, centroid height, and RMS width of the layer. We find that the annual variation of the height and width of the layer are essentially anti-correlated with previous measurements, while the column abundance lags its midlatitude counterpart by roughly three months. We suggest that the latitudinal differences in Fe layer properties result from variations in the distribution of mesospheric ozone and O2, which in turn affect the iron chemistry at the two latitudes.
BibTeX:
@article{Raizada2003,
  author = {Raizada, Shikha and Tepley, Craig A.},
  title = {Seasonal variation of mesospheric iron layers at Arecibo: First results from low-latitudes},
  journal = {Geophysical Research Letters},
  year = {2003},
  volume = {30},
  number = {2},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2002GL016537},
  doi = {10.1029/2002GL016537}
}
Sojka JJ, Thompson DC, Schunk RW, Eccles J, Makela JJ, Kelley MC, González SA, Aponte N and Bullett TW (2003), "Ionospheric data assimilation: recovery of strong mid-latitudinal density gradients ", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 65(10), pp. 1087 - 1097.
Abstract: The September 1999 Caribbean Ionospheric Campaign (CIC99), spanning the period 15–17 September 1999, was a period of repeated moderate geomagnetic storms. Both incoherent scatter radar (ISR) and digisonde F-layer measurements were made in the vicinity of Arecibo, Puerto Rico by the Arecibo ISR and Ramey Digisonde, which is one of the Digital Ionospheric Sounding System instruments. These data sets showed significant day-to-day F-layer variability, especially in the evening sectors. Local ionospheric data assimilation with the Assimilation Ionospheric Model (AIM1.06L) was able to reproduce this ionospheric day-to-day weather. However, during this time the Arecibo ISR was able to determine that strong latitude density gradients existed in the evening sector. These latitude gradients ranged from 5% to over 10% per degree of latitude, increasing equatorward. The climatological ionospheric forecast model (IFM) predicts gradients of the correct sign but significantly less than 5% per degree. Using the observed fact that the strong local vertical plasma drift was produced by an eastward electric field, an enhanced equatorial electric field model was created. This model was used to drive the IFM-E model. The effect of the enhanced electric field is to drive plasma flux tubes to higher latitudes and effectively move the poleward shoulder of the equatorial anomalies to higher latitudes. In this simulation, the simulated Arecibo density gradients range from 10% to 20% per degree. In addition, the local densities at Arecibo are now higher than the observed ones in the evening sector. The irony of this study is that the local AIM1.06L assimilation provides the correct local densities in the F region but is based upon the assumption of corotating field lines. When the plasma flux tubes are free to be E×B/B2 convected, as in the IFM equator model simulations, the local densities are too high. However, gradients in latitude are more realistic although somewhat larger than observed. This latter simulation is based on “better” physics than the AIM1.06L, but because the latitude (apex altitude) distribution of the eastward electric field driver is uncertain, it produces poor assimilation results. This study points to the need for more extended latitude coverage in the CIC campaigns in order to address the issue of a minimum data requirement for the assimilation.
BibTeX:
@article{Sojka20031087,
  author = {Jan J. Sojka and Donald C. Thompson and Robert W. Schunk and J.Vincent Eccles and Jonathan J. Makela and Michael C. Kelley and Sixto A. González and Nestor Aponte and Terence W. Bullett},
  title = {Ionospheric data assimilation: recovery of strong mid-latitudinal density gradients },
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2003},
  volume = {65},
  number = {10},
  pages = {1087 - 1097},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682603001652},
  doi = {10.1016/j.jastp.2003.07.004}
}
Sulzer M (2003), "RADAR | Incoherent Scatter Radar", In Encyclopedia of Atmospheric Sciences . Oxford , pp. 1812 - 1819. Academic Press.
BibTeX:
@incollection{Sulzer20031812,
  author = {M.P. Sulzer},
  editor = {Holton, James R. },
  title = {RADAR | Incoherent Scatter Radar},
  booktitle = {Encyclopedia of Atmospheric Sciences },
  publisher = {Academic Press},
  year = {2003},
  pages = {1812 - 1819},
  url = {http://www.sciencedirect.com/science/article/pii/B0122270908003304},
  doi = {10.1016/B0-12-227090-8/00330-4}
}
Tepley CA, Raizada S, Zhou Q and Friedman JS (2003), "First simultaneous observations of Ca+, K, and electron density using lidar and incoherent scatter radar at Arecibo", Geophysical Research Letters. Vol. 30(1), pp. 9-1/9-4.
Abstract: We report the first measurements of Ca+ made from the Arecibo Observatory achieved by using a frequency-agile resonance fluorescence lidar. Simultaneous observations of the electron concentration of the lower ionosphere using the Arecibo incoherent scatter radar were also made, as well as K lidar observations of the mesospause region. We find excellent agreement in the distribution of ions observed between the lidar and radar for both the thin tidal ion layers and for broader formations of ionization that occasionally occur near 90 km altitude. The concentration of Ca+ within ion layers was found to be slightly less than the relative fraction of calcium in meteors, and generally consistent with previous lidar, rocket, and twilight airglow measurements.
BibTeX:
@article{Tepley2003,
  author = {Tepley, Craig A. and Raizada, Shikha and Zhou, Qihou and Friedman, Jonathan S.},
  title = {First simultaneous observations of Ca+, K, and electron density using lidar and incoherent scatter radar at Arecibo},
  journal = {Geophysical Research Letters},
  year = {2003},
  volume = {30},
  number = {1},
  pages = {9-1/9-4},
  url = {http://dx.doi.org/10.1029/2002GL015927},
  doi = {10.1029/2002GL015927}
}
Tepley CA, Raizada S, Zhou Q and Friedman JS (2003), "Correction to “First simultaneous observations of Ca+, K, and electron density using lidar and incoherent scatter radar at Arecibo”", Geophysical Research Letters. Vol. 30(6), pp. n/a-n/a.
BibTeX:
@article{Tepley2003a,
  author = {Tepley, Craig A. and Raizada, Shikha and Zhou, Qihou and Friedman, Jonathan S.},
  title = {Correction to “First simultaneous observations of Ca+, K, and electron density using lidar and incoherent scatter radar at Arecibo”},
  journal = {Geophysical Research Letters},
  year = {2003},
  volume = {30},
  number = {6},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2003GL017188},
  doi = {10.1029/2003GL017188}
}
Titheridge JE (2003), "Ionisation below the night F2 layer - a global model", Journal of Atmospheric and Solar-Terrestrial Physics. Vol. 65(9), pp. 1035-1052.
BibTeX:
@article{Titheridge2003,
  author = {Titheridge, J E},
  title = {Ionisation below the night F2 layer - a global model},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
  year = {2003},
  volume = {65},
  number = {9},
  pages = {1035-1052},
  doi = {10.1016/S1364-6826(03)00136-6}
}
Vlasov MN, Kelley MC, Makela JJ and Nicolls MJ (2003), "Intense nighttime flux from the plasmasphere during a modest magnetic storm", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 65(10), pp. 1099 - 1105.
Abstract: An analytical-numerical model is created for two nights during Space Weather Month in September 1999. On one of these nights, after the midnight collapse over the Arecibo Observatory, the plasma density remained quite high in spite of a very sharp decrease in the F2 peak height. In order to support this high density against recombination, a very high plasma flux from the plasmasphere, a value of about 6×1e8cm-2s-1, is needed. Initially, data assimilation attempts did not allow such a flux (see Ionospheric data assimilation: recovery of strong mid-latitudinal density gradients, J. Atmos. Sol.-Terr. Phys., this issue). We believe the high flux results from a well-developed equatorial fountain and an Appleton anomaly well north of its usual location. The latter is consistent with both the large plasma gradient over Arecibo and the enhanced Jicamarca electric field (see Midlatitude plasma and electric field measurements during Space Weather Month, September 1999. J. Atmos. Sol.-Terr. Phys., this issue).
BibTeX:
@article{Vlasov2003,
  author = {Michael N. Vlasov and Michael C. Kelley and Jonathan J. Makela and Michael J. Nicolls},
  title = {Intense nighttime flux from the plasmasphere during a modest magnetic storm},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2003},
  volume = {65},
  number = {10},
  pages = {1099 - 1105},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682603001640},
  doi = {10.1016/j.jastp.2003.07.003}
}
Wilford CR, Moffett RJ, Rees JM, Bailey GJ and Gonzalez SA (2003), "Comparison of the He+ layer observed over Arecibo during solar maximum and solar minimum with CTIP model results", Journal of Geophysical Research: Space Physics. Vol. 108(A12), pp. n/a-n/a.
Abstract: Light ion concentration observations from the Arecibo incoherent scatter radar have shown regions of He+ layering in the topside ionosphere in the postmidnight hours. The He+ layering phenomenon has been observed during both solar maximum and solar minimum conditions. During solar maximum the layer is well defined, giving maximum relative abundances of over 50%. The observational results also show regions of He+ dominance in the topside ionosphere during solar maximum in the height range 750–1200 km. During solar minimum the magnitude of the layer is less, giving a maximum relative abundance of only ?20%; however, the layer is still a well-defined feature. The coupled thermosphere-ionosphere-plasmasphere (CTIP) model is shown to model accurately the He+ layer and the regions of He+ dominance, provided that the modeled temperature profiles are normalized to the observed values. This study serves to further highlight the importance of helium ions in the topside ionosphere, particularly during solar maximum nighttime conditions.
BibTeX:
@article{Wilford2003,
  author = {Wilford, C. R. and Moffett, R. J. and Rees, J. M. and Bailey, G. J. and Gonzalez, S. A.},
  title = {Comparison of the He+ layer observed over Arecibo during solar maximum and solar minimum with CTIP model results},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2003},
  volume = {108},
  number = {A12},
  pages = {n/a-n/a},
  url = {http://dx.doi.org/10.1029/2003JA009940},
  doi = {10.1029/2003JA009940}
}
Bishop R, Earle G, Gonzalez S, Sulzer M and Collins S (2002), "Inferred vertical ion velocities associated with intermediate layers ", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 64(12-14), pp. 1471-1477.
Abstract: This paper explores one aspect of ion–neutral coupling in the lower thermosphere. Using the continuity equation, we have developed a procedure to estimate the nighttime E-region vertical ion velocities from density observations obtained by the Arecibo Observatory. The technique is viable when adequate signal-to-noise ratios are present (e.g., when intermediate layers are present). Assuming that horizontal neutral winds are primarily responsible for intermediate layer observations, the calculated velocities may be used to infer information regarding the neutral wind field. The variations observed in the calculated vertical ion velocity may result from a variety of sources including fine-scale structures in the neutral wind, electric field effects or the coupling of the two.
BibTeX:
@article{Bishop2002,
  author = {R.L Bishop and G.D Earle and S.A Gonzalez and M.P Sulzer and S.C Collins},
  title = {Inferred vertical ion velocities associated with intermediate layers },
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2002},
  volume = {64},
  number = {12-14},
  pages = {1471-1477},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682602001116},
  doi = {10.1016/S1364-6826(02)00111-6}
}
Collins SC, Plane JM, Kelley MC, Wright TG, Soldán P, Kane TJ, Gerrard AJ, Grime BW, Rollason RJ, Friedman JS, Gonzalez SA, Zhou Q, Sulzer MP and Tepley CA (2002), "A study of the role of ion–molecule chemistry in the formation of sporadic sodium layers", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 64(7), pp. 845 - 860.
Abstract: Over two campaigns in 1998 and 1999, multiple sporadic sodium events were observed by the Arecibo Observatory sodium density lidar while simultaneously monitoring the plasma density using the incoherent scatter radar. In this paper, we test the theoretical explanation proposed by Cox and Plane (1998) where Na+ in a plasma layer is neutralized via an ion–molecule mechanism to form a sporadic sodium layer. A particular challenge is to interpret observations made in a Eulerian frame of observation where the spatial and temporal characteristics of events cannot easily be separated. The reaction scheme in the original mechanism is modified to include the reactions NaO++N2--Na+•N2+O and NaO++O2--Na++O3, following the results of theoretical quantum calculations. Six unique case studies of sporadic sodium layers are presented here, and excellent agreement between simulation and observations was obtained for five of them.
BibTeX:
@article{Collins2002a,
  author = {Stephen C. Collins and John M.C. Plane and Michael C. Kelley and Timothy G. Wright and Pavel Soldán and Timothy J. Kane and Andrew J. Gerrard and Brent W. Grime and Rosie J. Rollason and Jonathan S. Friedman and Sixto A. Gonzalez and Qihou Zhou and Michael P. Sulzer and Craig A. Tepley},
  title = {A study of the role of ion–molecule chemistry in the formation of sporadic sodium layers},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2002},
  volume = {64},
  number = {7},
  pages = {845 - 860},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682602001293},
  doi = {10.1016/S1364-6826(02)00129-3}
}
Friedman JS, Collins SC, Delgado R and Castleberg PA (2002), "Mesospheric potassium layer over the Arecibo Observatory, 18.3°N 66.75°W", Geophysical Research Letters. Vol. 29(5), pp. 15-1-15-4.
Abstract: A resonance lidar has made regular measurements of mesospheric potassium at the Arecibo Observatory (18.3°N, 66.75°W) since July 1999. Through July 2001 a total of 65 nights of density measurements were carried out, amounting to several nights each month over most of the period. The layer shows considerable nightly and seasonal variation: Spring and early summer nights had frequent sporadic layer activity; nightly variability in the layer width was large due to sporadic layer activity, but the seasonal variation was small; the altitude of the layer centroid was fairly constant throughout the year; and the column abundance showed semi-annual variation. These results are compared with a similar set of potassium measurements from a mid-latitude site, and the latitudinal implications are discussed.
BibTeX:
@article{Friedman2002,
  author = {Friedman, Jonathan S. and Collins, Stephen C. and Delgado, Rubén and Castleberg, Paul A.},
  title = {Mesospheric potassium layer over the Arecibo Observatory, 18.3°N 66.75°W},
  journal = {Geophysical Research Letters},
  year = {2002},
  volume = {29},
  number = {5},
  pages = {15-1-15-4},
  url = {http://dx.doi.org/10.1029/2001GL013542},
  doi = {10.1029/2001GL013542}
}
Kamalabadi F, Bust G, Dymond K, Gonzalez S, Bernhardt P, Chakrabarti S, Cotton D, Stephan A, McCoy R, Budzien S and Thonnard S (2002), "Tomographic studies of aeronomic phenomena using radio and UV techniques", Journal of Atmospheric and Solar-Terrestrial Physics. Vol. 64(12-14), pp. 1573-1580.
Abstract: Tomographic characterization of ionospheric and thermospheric structures using integrated line-of-sight measurements provides a unifying paradigm for the investigation of various aeronomic phenomena. In radio tomography, measurements of the total electron content (TEC) obtained using a chain of ground receivers and a transit satellite are inverted to reconstruct a two-dimensional electron density profile. Similarly, prominent optically thin UV emissions, such as 911 and produced by radiative recombination of O+, provide the means to obtain F-region electron densities from space-based spectroscopic measurements. The existence of a number of UV sensors in orbit and in planning stage provide the means to carry out such tomographic remote sensing investigations on global scales. The inherent non-ideal acquisition geometry of such remote sensing observations, however, results in limited-angle tomographic inverse problems that are both ill-posed and ill-conditioned. Furthermore, the intrinsic presence of noise, especially in the case of UV measurements, imposes challenges on conventional reconstruction methods. To overcome these limitations, we approach the solution of these inverse problems from a regularization standpoint. In particular, we apply regularization by incorporating appropriate edge-preserving regularizing functionals that enforce piecewise smoothness of the solution. This paper describes these techniques, investigates associated inversion issues, and demonstrates their applicability through a case study.
BibTeX:
@article{Kamalabadi2002,
  author = {Kamalabadi, Farzad and Bust, G. and Dymond, K. and Gonzalez, S. and Bernhardt, P. and Chakrabarti, S. and Cotton, D. and Stephan, A. and McCoy, R. and Budzien, S. and Thonnard, S.},
  title = {Tomographic studies of aeronomic phenomena using radio and UV techniques},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
  year = {2002},
  volume = {64},
  number = {12-14},
  pages = {1573-1580},
  url = {http://dx.doi.org/10.1016/s1364-6826(02)00096-2},
  doi = {10.1016/s1364-6826(02)00096-2}
}
Kelley M, Makela J and Saito A (2002), "The mid-latitude F region at the mesoscale: some progress at last", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 64(12–14), pp. 1525 - 1529.
Abstract: Almost no new theoretical work has been conducted in the area of mid-latitude F-region plasma instabilities since Perkin's (J. Geophys. Res. 78 (1973) 218) linear theory. New experimental data now suggest that the nonlinear development of mid-latitude F-region structures includes large polarization electric fields which dominate the final state. Airglow and radar data show that SumP is greatly depleted in some regions, which is in agreement with a polarization hypothesis. We hope these new results will inspire new simulations with some anticipation of solving this perplexing but fascinating problem.
BibTeX:
@article{Kelley2002,
  author = {M.C Kelley and J.J Makela and A Saito},
  title = {The mid-latitude F region at the mesoscale: some progress at last},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2002},
  volume = {64},
  number = {12–14},
  pages = {1525 - 1529},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682602000901},
  doi = {10.1016/S1364-6826(02)00090-1}
}
Meisel DD, Janches D and Mathews JD (2002), "Extrasolar Micrometeors Radiating from the Vicinity of the Local Interstellar Bubble", The Astrophysical Journal. Vol. 567, pp. 323-341.
Abstract: Over 12,000 micrometeor detections obtained mainly during 1997 November 15-20 and over a similar period in 1998 with the Arecibo UHF (430 MHz) radar have been processed so far. Out of this particular sample, nearly 3000 particles show measurable decelerations from which particle sizes can be estimated and extra-atmospheric velocities obtained by direct numerical integration through an appropriate MSIS model atmosphere. From this subsample, 143 objects that either had distinct 1 AU heliocentric hyperbolic orbits or were on elliptical orbits of high eccentricity with semimajor axes greater than 5 AU were found to have originally hyperbolic orbits at distances between 50 and 100 AU. Original extrasolar orbits, velocities, and radiants have been calculated by a Cowell-method, numerical integration back 10 yr into the past, when these particles first encountered the solar system at greater than 50 AU. The perturbation calculations included solar radiation pressure, solar wind magnetic field deflections, and the gravitational influence of Jupiter, Saturn, Uranus, and Neptune. The original extrasolar particle sample was parsed down in several ways to make a final list of interstellar particle (ISP) candidates. In Galactic coordinates relative to an assumed LSR (&alpha; = 18 h , &#240; = 30 &deg;, v = 20 km &deg;s -1 ), most of the remaining 108 ISP radiants form an extended cluster that appears to be coming from the region of the Local Bubble or the Local Cavity. In a new LSR determined by the mean ISP velocities, many of the particles appear to radiate from a region stretching from the Vela supernova to the vicinity of the Geminga pulsar. The Geminga supernova is a more likely source or transport agent of the Arecibo ISPs because of its greater age and relatively small distance from the Sun. The likelihood of a nearby supernova as an ISP source or at least an ISP transport mechanism is discussed is some detail. It is suggested that the Arecibo ISPs are samples at 1 AU of the particles detected earlier by the Pioneer 10 and 11 spacecraft between 5 and 18 AU.
BibTeX:
@article{Meisel2002,
  author = {David D. Meisel and Diego Janches and John. D. Mathews},
  title = {Extrasolar Micrometeors Radiating from the Vicinity of the Local Interstellar Bubble},
  journal = {The Astrophysical Journal},
  year = {2002},
  volume = {567},
  pages = {323-341},
  doi = {10.1086/322317}
}
Meisel DD, Janches D and Mathews JD (2002), "The Size Distribution of the Arecibo Interstellar Particles and Its Implications", The Astrophysical Journal. Vol. 579, pp. 895-904.
Abstract: Size histograms of all Arecibo ultra-high-frequency radar micrometeors detected in 1997-1998 whose radii were measured by atmospheric drag are presented. Most can be fitted with either a lognormal function or, alternatively, one or more power-law functions. Either form is indicative of significant fragmentation. The interplanetary dust particle (IDP) histogram results are discussed and compared with those considered to be extrasolar particles, including a subset of those deemed to be true interstellar particles (ISPs). The Arecibo IDP power-law results are shown to agree well with those derived from IRAS dust bands and Long-Duration Exposure Facility cratering, thus confirming the applicability of the sample to the derivation of mass estimates. A dichotomy between size histograms of particles with preperihelion Earth encounters and those with postperihelion encounters is evidence that significant size histogram change occurs when the smallest particles, including all ISPs, pass close to the Sun, even if only once. A small sample of previously undetected Arecibo postperihelion ISPs coming from the direction of the known Ulysses gas and dust flow are shown to have a size distribution and solar system dynamical properties similar to other Arecibo ISPs and therefore can be combined with previous ISP results to obtain a more robust sample. Derived mass flux points for the Arecibo ISPs agree well (over 5 orders of magnitude of mass) with a previously derived mass flux distribution function for Ulysses/Galileo spacecraft dust. This combined spacecraft and ground-based mass flux function is then used to infer a number of interesting mass-related solar system and astrophysical quantities.
BibTeX:
@article{Meisel2002a,
  author = {David D. Meisel and Diego Janches and John. D. Mathews},
  title = {The Size Distribution of the Arecibo Interstellar Particles and Its Implications},
  journal = {The Astrophysical Journal},
  year = {2002},
  volume = {579},
  pages = {895-904},
  doi = {10.1086/342919}
}
Pasko VP, Stanley M, Mathews JD, Inan US and Wood T (2002), "Electrical discharge from a thundercloud top to the lower ionosphere", Nature. Vol. 416, pp. 152-154.
Abstract: For over a century, numerous undocumented reports have appeared about unusual large-scale luminous phenomena above thunderclouds and, more than 80 years ago, it was suggested that an electrical discharge could bridge the gap between a thundercloud and the upper atmosphere. Since then, two classes of vertically extensive optical flashes above thunderclouds have been identified—sprites and blue jet. Sprites initiate near the base of the ionosphere, develop very rapidly downwards at speeds which can exceed 107 m s-1 , and assume many different geometrical forms. In contrast, blue jets develop upwards from cloud tops at speeds of the order of 105 m s-1 and are characterized by a blue conical shape. But no experimental data related to sprites or blue jets have been reported which conclusively indicate that they establish a direct path of electrical contact between a thundercloud and the lower ionosphere. Here we report a video recording of a blue jet propagating upwards from a thundercloud to an altitude of about 70 km, taken at the Arecibo Observatory, Puerto Rico. Above an altitude of 42 km—normally the upper limit for blue jets and the lower terminal altitude for sprites—the flash exhibited some features normally observed in sprites. As we observed this phenomenon above a relatively small thunderstorm cell, we speculate that it may be common and therefore represent an unaccounted for component of the global electric circuit.
BibTeX:
@article{Pasko2002,
  author = {Pasko, V. P. and Stanley, M. and Mathews, J. D and Umran S. Inan and Wood, T.},
  title = {Electrical discharge from a thundercloud top to the lower ionosphere},
  journal = {Nature},
  year = {2002},
  volume = {416},
  pages = {152-154},
  url = {http://www.nature.com/nature/journal/v416/n6877/full/416152a.html},
  doi = {10.1038/416152a}
}
Raizada S and Tepley CA (2002), "Iron Boltzmann lidar temperature and density observations from Arecibo - An initial comparison with other techniques", Geophysical Research Letters. Vol. 29(12), pp. 1-1/1-4.
Abstract: We introduce the first measurements of upper atmospheric temperature made from the Arecibo Observatory using the iron Boltzmann lidar technique. We use a single laser transmitter that can flip between two emissions every other pulse, which is suitable to observe the two iron transitions within the same region of space. Comparisons are made with airglow measurements and the MSIS-90 model to estimate temperature, and with incoherent scatter radar observations to associate the structure of electron concentration with enhancements observed in the concentration of neutral iron. We find good agreement between lidar and airglow derived temperatures near the mesopause, while the model tends to underestimate the thermal depth of the mesopause at Arecibo compared with observations. In addition, simultaneous temperatures measured via lidar and airglow may help to clarify the heights where the airglow emissions occur.
BibTeX:
@article{Raizada2002,
  author = {Raizada, Shikha and Tepley, Craig A.},
  title = {Iron Boltzmann lidar temperature and density observations from Arecibo - An initial comparison with other techniques},
  journal = {Geophysical Research Letters},
  year = {2002},
  volume = {29},
  number = {12},
  pages = {1-1/1-4},
  url = {http://dx.doi.org/10.1029/2001GL014535},
  doi = {10.1029/2001GL014535}
}
Zhou QH (2002), "Incoherent scatter spectral bandwidth and its applications", Radio Science. Vol. 37(3), pp. 18-1-18-9.
Abstract: We derive an analytical expression of equivalent incoherent scatter spectral bandwidth and discuss its practical and interpretative usefulness at different altitude ranges. In the region above 120 km, where collision can be neglected, the equivalent bandwidth is a simple function of electron and ion temperature, ion mass, and ion composition. In the collision-dominated D region, equivalent bandwidth can be used to conveniently assess the effect of negative ions. As an example to illustrate the usefulness of the equivalent bandwidth, we also present nighttime incoherent scatter E region temperature measurement, which has not been reported previously for middle and low latitudes.
BibTeX:
@article{RDS:RDS4686,
  author = {Zhou, Qihou H.},
  title = {Incoherent scatter spectral bandwidth and its applications},
  journal = {Radio Science},
  year = {2002},
  volume = {37},
  number = {3},
  pages = {18-1--18-9},
  url = {http://dx.doi.org/10.1029/2000RS002589},
  doi = {10.1029/2000RS002589}
}
Sethi NK and Mahajan KK (2002), "The bottomside parameters B0,B1 obtained from incoherent scatter measurements during a solar maximum and their comparisons with the IRI-2001 model", Annales Geophysicae. Vol. 20, pp. 817-822.
BibTeX:
@article{Sethi2002,
  author = {Sethi, N K and Mahajan, K K},
  title = {The bottomside parameters B0,B1 obtained from incoherent scatter measurements during a solar maximum and their comparisons with the IRI-2001 model},
  journal = {Annales Geophysicae},
  year = {2002},
  volume = {20},
  pages = {817-822},
  doi = {10.5194/angeo-20-817-2002}
}
Starks MJ (2002), "Effects of HF heater-produced ionospheric depletions on the ducting of VLF transmissions: A ray tracing study", Journal of Geophysical Research: Space Physics. Vol. 107(A11), pp. SIA 3-1/SIA 3-9.
BibTeX:
@article{Starks2002,
  author = {Starks, M. J.},
  title = {Effects of HF heater-produced ionospheric depletions on the ducting of VLF transmissions: A ray tracing study},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2002},
  volume = {107},
  number = {A11},
  pages = {SIA 3-1/SIA 3-9},
  doi = {10.1029/2001JA009197}
}
Swartz WE, Collins SC, Kelley MC, Makela JJ, Kudeki E, Franke S, Urbina J, Aponte N, González S, Sulzer MP and Friedman JS (2002), "First observations of an F-region turbulent upwelling coincident with severe E-region plasma and neutral atmosphere perturbations ", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 64(12–14), pp. 1545 - 1556.
Abstract: Highly structured electron densities in the E and F regions over Puerto Rico during the night of February 20/21, 1999 were accompanied by intense coherent VHF radar backscatter from the E region and perturbations in neutral sodium in the mesosphere. Simultaneous observations of the event were made with the VHF Cornell University Portable Radar Interferometer (CUPRI) located near Isabela, PR, the University of Illinois VHF radar located at Salinas, PR, the Arecibo incoherent scatter radar, and the sodium lidar located at the Arecibo Observatory. On this geomagnetically quiet night, regions of very different electron concentrations moved through the region. The F-region peak altitudes of the low density regions differed by about 100 km from the high-density region altitudes. The E region also exhibited an unusual enhancement with a vertical extent of about 6 km and caused intense VHF backscatter. The echoing E regions seen by both VHF radars were highly structured with multiple filaments and Doppler shifts exceeding 300 m/s (directed north and upward) some of the time. The Arecibo incoherent scatter radar recorded a large eastward component of the velocity (?200 m/s) during the early portion of the event, which then switched to strongly westward (peaking over 500 m/s and averaging perhaps 400 m/s for about half an hour) before returning eastward. The meridional velocity components were also variable. The Arecibo lidar showed an intense sodium layer that maintained a constant altitude until the strongest VHF echoes began. Then the layer fell 2 km over a time span of about half an hour and the lidar echoes intensified. Because (1) the timing of the events at the different locations is well correlated with the F-region drifts as measured with the Arecibo radar, and (2) because the Pedersen conductivity falls precipitiously at the start of the event, we conclude there was strong coupling between the E and F regions, perhaps even reaching the mesosphere, during this event. However, major problems may remain. How can the E-region cloud track the F-region blob when supposedly it is coupled to the neutrals? Does the neutral wind track the F-region ion velocity? We do not think so, but this is the easiest solution.
BibTeX:
@article{Swartz20021545,
  author = {Wesley E. Swartz and Stephen C. Collins and Michael C. Kelley and Jonathan J. Makela and Erhan Kudeki and Steve Franke and Julio Urbina and Nestor Aponte and Sixto González and Michael P. Sulzer and Jonathan S. Friedman},
  title = {First observations of an F-region turbulent upwelling coincident with severe E-region plasma and neutral atmosphere perturbations },
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2002},
  volume = {64},
  number = {12–14},
  pages = {1545 - 1556},
  note = {Equatorial Aeronomy },
  url = {http://www.sciencedirect.com/science/article/pii/S1364682602000925},
  doi = {10.1016/S1364-6826(02)00092-5}
}
Aponte N, Sulzer MP and Gonzalez SA (2001), "Corection of the Jicamarca electron-ion temperature ratio problem: Verifying the effect of electron Coulomb collisions on the incoherent scatter spectrum", Journal of Geophysical Research: Space Physics. Vol. 106(A11), pp. 24785-24793.
Abstract: Ever since the first attempts to fit Jicamarca autocorrelation function (ACF) measurements in the 1970s using a full nonlinear least squares analysis, an apparent electron-ion temperature ratio below unity has been deduced for a large portion of the F region data. The cause of this unexpected and geophysically unreasonable result has been a mystery until recently, when Sulzer and Gonzalez [1999] (herein SG) explained how electron Coulomb collisions can distort, or narrow, the incoherent backscatter spectrum, and that for this narrowing to be observable two conditions must be met. First, the radar k vector must lie in a small range near perpendicular to the magnetic field, and second, the radar wavelength must be sufficiently long. Both of these conditions are true at Jicamarca. The accurate calculations from the SG theory are now available in a compact library, which we have incorporated into an incoherent scatter least squares fitting code. Using this code, we have reduced Jicamarca ACF data taken with the Faraday double-pulse mode, and find that the SG theory correctly interprets the ACF data from Jicamarca, thereby solving the longstanding Te/Ti ratio problem and thus allowing accurate electron and ion temperature measurements.
BibTeX:
@article{Aponte2001,
  author = {Aponte, Néstor and Sulzer, Michael P. and Gonzalez, Sixto A.},
  title = {Corection of the Jicamarca electron-ion temperature ratio problem: Verifying the effect of electron Coulomb collisions on the incoherent scatter spectrum},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2001},
  volume = {106},
  number = {A11},
  pages = {24785-24793},
  url = {http://dx.doi.org/10.1029/2001JA000103},
  doi = {10.1029/2001JA000103}
}
Gorgolewski S and Rozej B (2001), "Evidence for electrotropism in some plant species", Advances in Space Research . Vol. 28(4), pp. 633-638.
BibTeX:
@article{Gorgolewski2001,
  author = {S Gorgolewski and B Rozej},
  title = {Evidence for electrotropism in some plant species},
  journal = {Advances in Space Research },
  year = {2001},
  volume = {28},
  number = {4},
  pages = {633-638},
  doi = {10.1016/S0273-1177(01)00371-4}
}
Hickey MP (2001), "Reflection of a long-period gravity wave observed in the nightglow over Arecibo on May 8–9, 1989?", Journal of Geophysical Research: Atmospheres. Vol. 106(D22), pp. 28199-28208.
Abstract: During the Arecibo Initiative for Dynamics of the Atmosphere (AIDA) campaign in 1989 a characteristic of gravity wave perturbations observed in mesopause region airglow emissions was that airglow brightness fluctuations and airglow-derived temperature fluctuations often occurred either in phase or in antiphase. This stimulated the development of a theory suggesting that such in-phase fluctuations were most probably the result of strong reflections occurring in the mesosphere and lower thermosphere region. Recent examination of a particular wave event and application of simple WKB-type theory has appeared to support this hypothesis. Here we use a full-wave model and a WKB-type model, each coupled with a chemical-airglow fluctuation model describing O2 atmospheric and OH Meinel airglow fluctuations, to assess the strength of wave reflection and also to explicitly calculate the phase difference between the airglow brightness and the temperature fluctuations. Our results suggest that reflection is not strong for the particular wave event, and the model produces fairly large phase differences between the airglow brightness and the temperature fluctuations (?35° and ?134°–165° for the O2 atmospheric and OH airglow emissions, respectively). These results are not particularly sensitive to the nominal mean winds used in the simulations. There is an instance when a region of minimum refractive index occurs directly above a region in which reflection is strongest, suggesting that the two are related. However, the reflection does not appear to be strong. Our results suggest that chemical effects can account for the inferred phases of the observed airglow fluctuations and that effects associated with wave reflection appear to play a relatively minor role in the airglow fluctuations.
BibTeX:
@article{Hickey2001,
  author = {Hickey, Michael P.},
  title = {Reflection of a long-period gravity wave observed in the nightglow over Arecibo on May 8–9, 1989?},
  journal = {Journal of Geophysical Research: Atmospheres},
  year = {2001},
  volume = {106},
  number = {D22},
  pages = {28199-28208},
  url = {http://dx.doi.org/10.1029/2001JD900221},
  doi = {10.1029/2001JD900221}
}
Janches D, Meisel DD and Mathews JD (2001), "Orbital Properties of the Arecibo Micrometeoroids at Earth Interception", Icarus. Vol. 150, pp. 206-218. Elsevier Science.
Abstract: Using the Arecibo Observatory (AO) 430-MHz Radar we have developed a Doppler technique to measure very precise micrometeor instantaneous velocities directly from the meteor head echo. In addition, a large number of the observed meteoroids show deceleration. With the velocity, the deceleration, and the assumptions of a spherical shape and a mean micrometeoroid mass density, we have obtained estimates of in-atmosphere particle sizes. The size estimate, the MSIS model atmosphere, and the measured deceleration are used to obtain the meteor extra-atmospheric speeds, assuming these particles undergo little mass-loss prior to and during the time we detect them (Janches et al. 2000b, Icarus145, 53–63). Orbital elements at 1 AU are presented and discussed. These results have not been corrected for perturbation effects such as radiation pressure, Poynting–Robertson drag, attraction by the giant planets, and photoelectric charging effects. So far, over 7700 detections obtained during November 1997 and 3500 during the November 1998 observation campaigns have been analyzed. The observing periods included the Leonids meteor shower, but none of the orbits are recently derived from it. Out of these detections, we present details of over 1500 orbits with eccentricities less than unity. These orbits show (a) a depletion of postperihelion particles with small perihelion distance, suggesting the possibility of collisional and thermal destruction, and (b) an enhancement of particles with perihelia in the zone between Mercury and Venus. Also discussed are 40 betha-meteoroids (with radii less than 0.5 um) dynamically related to the elliptical orbit population with q<0.7 AU. We interpret the latter results on the basis of Poynting–Robertson drag and the electromagnetic resonant effects proposed by G. E. Morfill and E. Grun (1979, Planet. Space Sci.27, 1269–1282). Comparison with previous data sets indicates that most of the AO micrometeoroid orbits are well randomized and that association with a particular parent body is unlikely.
BibTeX:
@article{Janches2001,
  author = {Janches, D and Meisel, D D and Mathews, J D},
  title = {Orbital Properties of the Arecibo Micrometeoroids at Earth Interception},
  journal = {Icarus},
  publisher = {Elsevier Science},
  year = {2001},
  volume = {150},
  pages = {206-218},
  url = {http://dx.doi.org/10.1006/icar.2000.6575},
  doi = {10.1006/icar.2000.6575}
}
Kane T, Grime B, Franke S, Kudeki E, Urbina J, Kelley M and Collins S (2001), "Joint observations of sodium enhancements and field-aligned ionospheric irregularities", Geophysical Research Letters. Vol. 28(7), pp. 1375-1378.
Abstract: Resonance Lidar observations of neutral sodium and VHF coherent scatter radar observations of field-aligned 3-meter irregularities were obtained during the Coqui II rocket campaign in Puerto Rico. The Lidar, a facility instrument at the Arecibo Observatory (18.3°N, 66.8°W), and the University of Illinois Radar, located near Salinas on the south of the island, both monitored volumes near where the uplegs of the nominal rocket trajectories intersected the E-region. The Observatory's Incoherent Scatter Radar was also used to characterize the plasma layers. Preliminary investigation of the data sets has shown a potential correspondence between VHF backscatter from plasma layers and a new class of characteristic enhancements in the neutral sodium.
BibTeX:
@article{Kane2001,
  author = {Kane, T. and Grime, B. and Franke, S. and Kudeki, E. and Urbina, J. and Kelley, M. and Collins, S.},
  title = {Joint observations of sodium enhancements and field-aligned ionospheric irregularities},
  journal = {Geophysical Research Letters},
  year = {2001},
  volume = {28},
  number = {7},
  pages = {1375-1378},
  url = {http://dx.doi.org/10.1029/2000GL012176},
  doi = {10.1029/2000GL012176}
}
Kerr RB, Garcia R, He X, Noto J, Lancaster RS, Tepley CA, Gonzalez SA, Friedman J, Doe RA, Lappen M and McCormack B (2001), "Secular variability of the geocoronal Balmer-alpha brightness: magnetic activity and possible human influences", Journal of Geophysical Research: Space Physics. Vol. 106(A12), pp. 28819-28830.
Abstract: Measurements of the geocoronal Balmer-alpha (H&alpha;) brightness taken between 1983 and 1994 at the Arecibo Observatory (18.35° N, 66.75° W) occasionally display aperiodic brightness variations that we attribute to a local response of exospheric hydrogen abundance to geomagnetic activity. Approximately twofold H&alpha; brightness enhancements in the days following moderate storm onset conditions are demonstrated, and the absolute brightness during these events is significantly greater than modeled brightness based on quiet geomagnetic conditions. Although there are no direct measurements of the line center solar Lyman beta (Ly &beta;) flux that pumps H&alpha; during these events, the magnitude of the brightness enhancements and the temporal reproducibility of the phenomena (following onset of all storms in our data) make it likely that the enhanced H&alpha; brightness is due to enhanced column abundances of hydrogen in the exosphere above Arecibo and not to sporadic increases in the solar Ly &beta; flux. Increased hydrogen abundance due to thermal expansion of the midlatitude atmosphere following propagation of the auroral heating event cannot account for the entire enhancement. The data also suggest that H&alpha;. brightness has become systematically stronger from 1984 to 1994, independent of solar cycle variability or variations due to geomagnetic activity. An increase of ~3% per year, may be attributable to real change in the geocoronal hydrogen column abundance during the period, and is possibly a consequence of increasing hydrogenous species concentrations in the lower atmosphere. The enhancement of geocoronal H&alpha; brightness between 1984 and 1994 may be the consequence of increasing methane in the troposphere and may signal that the effects of methane deposition in the lower atmosphere have propagated throughout the atmosphere.
BibTeX:
@article{Kerr2001,
  author = {Kerr, R. B. and Garcia, R. and He, X. and Noto, J. and Lancaster, R. S. and Tepley, C. A. and Gonzalez, S. A. and Friedman, J. and Doe, R. A. and Lappen, M. and McCormack, B.},
  title = {Secular variability of the geocoronal Balmer-alpha brightness: magnetic activity and possible human influences},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2001},
  volume = {106},
  number = {A12},
  pages = {28819-28830},
  url = {http://dx.doi.org/10.1029/1999JA900187},
  doi = {10.1029/1999JA900187}
}
Kerr RB, Garcia R, He X, Noto J, Lancaster RS, Tepley CA, Gonzalez SA, Friedman J, Doe RA, Lappen M and McCormack B (2001), "Periodic variations of geocoronal Balmer-alpha brightness due to solar-driven exospheric abundance variations", Journal of Geophysical Research: Space Physics. Vol. 106(A12), pp. 28797-28817.
Abstract: Measurements of the geocoronal Balmer-alpha (H&alpha;) brightness have been made at the Arecibo Observatory during 11 separate periods since 1983 using both a Fabry-Perot interferometer and a tilting filter photometer. The tilting filter photometer is calibrated for absolute sensitivity using a constant brightness source traceable to National Institute of Standards and Techniques (NIST) standards and is used to cross-calibrate the Fabry-Perot interferometer. Since the observational technique has not changed since 1983, and since the data analyses technique are uniform, these data provide a measure of the solar cycle variation of H&alpha; brightness at Arecibo. Unlike earlier studies, we discern no systematic discrepancy between the H&alpha; brightness and estimates of the solar Lyman-beta flux that pumps the resonant fluorescent H&alpha; emission. Rather, we conclude that geocoronal hydrogen abundance is generally (but not always) larger than models suggest, although not systematically so. The largest H&alpha; emission is measured during solar minimum conditions, when brightness is approximately 50% greater than during solar maximum conditions, for measurements at solar depression angles from 15° to 35°. Above about 40° solar depression (corresponding to an illuminated column with a base at approximately 2000 km), no solar cycle variation is evident, and the brightness there is persistently greater than models. Intricacies of the Lyman-beta radiative transport problem make detection of an early morning maximum of hydrogen density near the exobase difficult using brightness data alone, although the H&alpha; brightness is generally asymmetric with respect to local midnight, with brighter emission in the postmidnight sector. Studies of the semidiurnal (nighttime) variation demonstrate that the H&alpha; brightness can vary by a factor of 2 over a period of days.
BibTeX:
@article{Kerr2001a,
  author = {Kerr, R. B. and Garcia, R. and He, X. and Noto, J. and Lancaster, R. S. and Tepley, C. A. and Gonzalez, S. A. and Friedman, J. and Doe, R. A. and Lappen, M. and McCormack, B.},
  title = {Periodic variations of geocoronal Balmer-alpha brightness due to solar-driven exospheric abundance variations},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2001},
  volume = {106},
  number = {A12},
  pages = {28797-28817},
  url = {http://dx.doi.org/10.1029/1999JA900186},
  doi = {10.1029/1999JA900186}
}
Leyser T (2001), "Stimulated electromagnetic emissions by high-frequency electromagnetic pumping of the ionospheric plasma", Space Science Reviews. Vol. 98(3-4), pp. 223-328.
BibTeX:
@article{Leyser2001,
  author = {Leyser, T.B.},
  title = {Stimulated electromagnetic emissions by high-frequency electromagnetic pumping of the ionospheric plasma},
  journal = {Space Science Reviews},
  year = {2001},
  volume = {98},
  number = {3-4},
  pages = {223-328},
  doi = {10.1023/A:1013875603938}
}
Machuga D and Mathews J (2001), "Numerical simulations of three-dimensional E-region ion trajectories in realistic tidal wind and E-field structures: layer formation and transport", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 63(14), pp. 1519-1528.
BibTeX:
@article{Machuga2001,
  author = {D.W. Machuga and J.D. Mathews},
  title = {Numerical simulations of three-dimensional E-region ion trajectories in realistic tidal wind and E-field structures: layer formation and transport},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2001},
  volume = {63},
  number = {14},
  pages = {1519-1528},
  doi = {10.1016/S1364-6826(01)00033-5}
}
Mahajan KK and Sethi N (2001), "Empirical models of parameters B0, B1 from Arecibo radar measurements", Advances in Space Research. Vol. 27, pp. 17-20.
BibTeX:
@article{Mahajan2001,
  author = {Mahajan, K K and Sethi, N},
  title = {Empirical models of parameters B0, B1 from Arecibo radar measurements},
  journal = {Advances in Space Research},
  year = {2001},
  volume = {27},
  pages = {17-20},
  doi = {10.1016/S0273-1177(00)00135-6}
}
Makela JJ, Kelley MC, Gonzalez SA, Aponte N and McCoy RP (2001), "Ionospheric topography maps using multiple-wavelength all-sky images", Journal of Geophysical Research: Space Physics. Vol. 106(A12), pp. 29161-29174.
Abstract: We outline a technique to create three-dimensional topographic maps of the Earth's ionosphere. Using all-sky images at 630.0 and 777.4 nm taken with the Cornell All-Sky Imager (CASI) while located at the Arecibo Observatory, we can estimate the maximum density (Nm) and the height (Hm) of the F layer over a 1000 × 1000 km area. This is possible because to first order, the 777.4 nm emission, produced by radiative recombination, is proportional to the integral of the square of the plasma density, whereas the 630.0 nm line, produced by charge exchange and dissociative recombination, depends on both plasma height and density. Using the neutral atmosphere given by the Mass Spectrometer Incoherent Scatter (MSIS-86) model and electron densities from the international reference ionosphere 1995 (IRI-95) model, we show that the estimates given by these maps are good to within 5% of the values used as input into the models. These errors are slightly larger (10%) when extreme gradients in the height of the F layer are present. We apply our technique to two different nights in 1999. In one example these maps show a steeply rising ridge of ionization stretching equatorward of the Caribbean site, punctuated by a series of parallel ridges and valleys. We compare these observations with previous work at Arecibo during very high magnetic activity. In our case we find no evidence for particle precipitation and agree with Sahai et al. [1981a] that spatial variations may have affected the earlier study. Another example shows the Appleton anomaly much farther north than normal. Instability processes are indicated in the former case, while physical mechanisms associated with a magnetic storm are explored in the latter case.
BibTeX:
@article{Makela2001,
  author = {Makela, Jonathan J. and Kelley, Michael C. and Gonzalez, Sixto A. and Aponte, Nestor and McCoy, Robert P.},
  title = {Ionospheric topography maps using multiple-wavelength all-sky images},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2001},
  volume = {106},
  number = {A12},
  pages = {29161-29174},
  url = {http://dx.doi.org/10.1029/2000JA000449},
  doi = {10.1029/2000JA000449}
}
Makela JJ, Kelley MC, Sojka JJ, Pi X and Mannucci AJ (2001), "GPS normalization and preliminary modeling results of total electron content during a midlatitude space weather event", Radio Science. Vol. 36(2), pp. 351-361.
Abstract: On November 22–23, 1997, a geomagnetic storm occurred during a period of excellent viewing conditions over the Arecibo Observatory in Puerto Rico. Here we explore the total electron content (TEC) registered by Global Positioning System (GPS) receivers located close to the Cornell All-Sky Imager (CASI) at the Arecibo Observatory. The storm began with the equatorward surge of a very high (100% increase) TEC enhancement stretching for many hours of local time on the dayside. At dusk the TEC over the Caribbean remained elevated with levels equal to the noontime monthly averages. During the event the TEC was highly structured and clearly correlated with high and low airglow emission levels. In one fortuitous instance a common ionospheric penetration point (15 km apart), shared by two GPS satellites viewed from two receiving stations, registered an 8 TEC unit difference during the active period. We show that a GPS station can be calibrated using the pseudorange method and a reliable data-driven technique during quiet conditions and still have absolute TEC capability within 2 TEC units (RMS) 5 days later. We compare the observations to a climatological model which, although reasonable for quiet times, is very poor during the storm period. We also present an independent evaluation of the GPS TEC. This study is an initial step toward quality control of this database, needed before it is used in an assimilation model.
Review: On November 22–23, 1997, a geomagnetic storm occurred during a period of excellent viewing conditions over the Arecibo Observatory in Puerto Rico. Here we explore the total electron content (TEC) registered by Global Positioning System (GPS) receivers located close to the Cornell All-Sky Imager (CASI) at the Arecibo Observatory. The storm began with the equatorward surge of a very high (100% increase) TEC enhancement stretching for many hours of local time on the dayside. At dusk the TEC over the Caribbean remained elevated with levels equal to the noontime monthly averages. During the event the TEC was highly structured and clearly correlated with high and low airglow emission levels. In one fortuitous instance a common ionospheric penetration point (15 km apart), shared by two GPS satellites viewed from two receiving stations, registered an 8 TEC unit difference during the active period. We show that a GPS station can be calibrated using the pseudorange method and a reliable data-driven technique during quiet conditions and still have absolute TEC capability within 2 TEC units (RMS) 5 days later. We compare the observations to a climatological model which, although reasonable for quiet times, is very poor during the storm period. We also present an independent evaluation of the GPS TEC. This study is an initial step toward quality control of this database, needed before it is used in an assimilation model.
BibTeX:
@article{Makela2001a,
  author = {Makela, Jonathan J. and Kelley, Michael C. and Sojka, Jan J. and Pi, Xiaoqing and Mannucci, Anthony J.},
  title = {GPS normalization and preliminary modeling results of total electron content during a midlatitude space weather event},
  journal = {Radio Science},
  year = {2001},
  volume = {36},
  number = {2},
  pages = {351-361},
  url = {http://dx.doi.org/10.1029/1999RS002427},
  doi = {10.1029/1999RS002427}
}
Mathews JD, Janches D, Meisel DD and Zhou QH (2001), "The micrometeoroid mass flux into the upper atmosphere: Arecibo results and a comparison with prior estimates", Geophysical Research Letters. Vol. 28(10), pp. 1929-1932.
Abstract: Radar micrometeor observations at Arecibo Observatory have enabled direct estimates of the meteoroid mass flux into the upper atmosphere. We report mass flux determinations from November 1997/1998 observations that are based on the observed number of meteor events per day in the 300 m diameter Arecibo beam and on particle mass determinations from that fraction of all particles for which deceleration is measured. The average mass of the Arecibo micrometeoroids that manifest observable deceleration is ~0.32/0.76 µgm/particle with a resultant annual whole Earth mass flux of 1.6 × 106/2.7 × 106 kg/yr over the ~10-5-10² µgm mass range for 1997/1998, respectively. The annual whole earth mass flux per decade of particle mass is calculated and compared with that of Ceplecha et al. [1998] (3.7 × 106 kg/yr) and with that derived by Love and Brownlee [1993] (LB) from small particle impact craters on the orbital Long Duration Exposure Facility (LDEF). We also give the LDEF results as significantly modified using the Arecibo determined average particle velocity of ~50 km/sec-much larger than the effective value of 12 km/sec used by LB. This modification results in a net LDEF mass flux of 1.8×106 kg/yr 7% of the value we determined from reanalysis of the LB data using their original 12 km/sec mean impact speed. These results may provoke some debate.
BibTeX:
@article{Mathews2001,
  author = {Mathews, J. D. and Janches, D. and Meisel, D. D. and Zhou, Q -H.},
  title = {The micrometeoroid mass flux into the upper atmosphere: Arecibo results and a comparison with prior estimates},
  journal = {Geophysical Research Letters},
  year = {2001},
  volume = {28},
  number = {10},
  pages = {1929-1932},
  url = {http://dx.doi.org/10.1029/2000GL012621},
  doi = {10.1029/2000GL012621}
}
Mathews JD, Gonzalez S, Sulzer MP, Zhou Q-H, Urbina J, Kudeki E and Franke S (2001), "Kilometer-scale layered structures inside spread-F", Geophysical Research Letters. Vol. 28(22), pp. 4167-4170.
Abstract: We report the first incoherent scatter radar observations—made at Arecibo Observatory—of remarkable bottom-side (<280 km) F-region sheet-like plasma structures with horizontal/vertical-scales of ~1 km. These structures are an apparent manifestation of spread-F, appear to give rise to VHF coherent (FAI) scattering, and are clearly electrodynamic in origin involving a form of the Perkins spread-F instability process in the presence of relatively large E-fields and horizontal plasma gradients. The net instability process appears to be associated with downwelling features characteristic of the nighttime F-region. These structures—that may be self-similar on scales of ~1–100 km—indicate considerable electrodynamic activity in the mid-latitude F-region on scales that have profound space-weather implications especially regarding deep scintillations on earth-space communications links.
BibTeX:
@article{Mathews2001a,
  author = {Mathews, J. D. and Gonzalez, S. and Sulzer, M. P. and Zhou, Q.-H. and Urbina, J. and Kudeki, E. and Franke, S.},
  title = {Kilometer-scale layered structures inside spread-F},
  journal = {Geophysical Research Letters},
  year = {2001},
  volume = {28},
  number = {22},
  pages = {4167-4170},
  url = {http://dx.doi.org/10.1029/2001GL013077},
  doi = {10.1029/2001GL013077}
}
Mathews J, Machuga D and Zhou Q (2001), "Evidence for electrodynamic linkages between spread-F, ion rain, the intermediate layer, and sporadic E: results from observations and simulations", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 63(14), pp. 1529-1543.
Abstract: High resolution ISR observations of the evening and nighttime E- and F-regions at Arecibo during both “normal” low-activity periods and during an active spread-F event reveal apparent electrodynamic links between the low-lying layers, ion-rain, and the spread-F instability process. In particular, during a 22 November 1994 event, streaks of ionization—ion rain [Mathews et al., Geophys. Res. Lett. 24 (1997) 1411]—appear to descend from the highly structured F-region base onto the 100-110 Tidal Ion Layer (TIL) system. The evening intermediate tidal ion layer, if present, is almost totally disrupted while the spread-F event is characterized by deep, almost vertical folds in electron concentration. The amplitudes of these structures are 100% with fold-structures extending from the nominal F-region base to well above the nominal peak of the F-region. Apparent periods range from less than 10min for small-scale structures to about 40min for the largest-scales. We suggest that the E-region structures are a manifestation of polarization electric fields that “map” into the E-region and are well in excess of 1mV/m in contrast to low-activity period small-scale fields of order 1mV/m. These E-fields are hypothesized to be generated in the “field” of linear (low-activity) and/or non-linear (high-activity spread-F periods) Perkins-like instabilities that are individually of relatively small horizontal-scales but occur over large horizontal distances in the bottom-side of the nighttime F-region. We present numerical simulations of 3-dimensional ion trajectories in tidal wind and electric field structures similar to those implied by these observations. These simulations extend the results of Machuga and Mathews (J. Atmos. Solar-Terres. Phys., 2001, 63(14), 1519–1528, this issue.) (Paper I) and demonstrate the formation of parallel sheets of ionization that form in the tilted plane oriented transverse to the bulk flow of the F-region that sweeps ~1mV/m amplitude E-fields quasi-periodically through a fixed location in the E-region. A fixed pointing radar sees these ionization sheets as ion-rain-like features.
BibTeX:
@article{Mathews2001b,
  author = {J.D. Mathews and D.W. Machuga and Q. Zhou},
  title = {Evidence for electrodynamic linkages between spread-F, ion rain, the intermediate layer, and sporadic E: results from observations and simulations},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2001},
  volume = {63},
  number = {14},
  pages = {1529-1543},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682601000347},
  doi = {10.1016/S1364-6826(01)00034-7}
}
Meléndez-Alvira DJ, Picone JM, Kelley OA, Zhou Q and Sulzer MP (2001), "Bimodality in the climatological topside electron and exospheric temperature distributions at Arecibo", Radio Science. Vol. 36(2), pp. 311-324.
Abstract: We report on the local time, occurrence frequency, and solar activity variations of the measured electron temperature and the ratio of the electron to ion temperatures at 589 km, and the inferred exospheric neutral temperatures. The World Day measurements at Arecibo, Puerto Rico, were made between 1985 and 1995, spanning both solar maximum and minimum conditions during predominantly quiet geomagnetic conditions. Histograms of the electron and exospheric temperatures reveal bimodal distributions. The electron temperature bimodality is primarily due to the sharp difference between daytime and nighttime temperatures whereas the exospheric temperature bimodality is primarily due to the difference between high and low solar activity. The nighttime exosphere and the electrons at 589 km are hotter by up to 400 K during high solar activity than during low solar activity. The daytime electrons at 589 km are, however, colder after 0800 LT during high solar activity than during low solar activity. The daytime ratio of electron to ion temperatures is also lower at high solar activity but not until after 1000 LT on average. Unlike the electron temperature at 589 km, the distribution of the electron to ion temperatures is unimodal.
BibTeX:
@article{Melendez-Alvira2001,
  author = {Meléndez-Alvira, D. J. and Picone, J. M. and Kelley, O. A. and Zhou, Q. and Sulzer, M. P.},
  title = {Bimodality in the climatological topside electron and exospheric temperature distributions at Arecibo},
  journal = {Radio Science},
  year = {2001},
  volume = {36},
  number = {2},
  pages = {311-324},
  url = {http://dx.doi.org/10.1029/2000RS002435},
  doi = {10.1029/2000RS002435}
}
Pandey V, Sethi N and Mahajan K (2001), "Equivalent slab thickness and its variability: a study with incoherent scatter measurements", Advances in Space Research . Vol. 27(1), pp. 60-64.
Abstract: In order to check its usefulness for the IRI, incoherent scatter (I.S.) radar measurements at Arecibo (18.4° N, 66.7° W), for the solar minimum period of 1974–1977 are used to study equivalent slab thickness (EST) and its variability. While systematic diurnal changes are apparent, day-to-day and hour-to-hour fluctuations can also not be overlooked. This variability is examined in relation to the simultaneously measured F-layer peak height and electron temperature. While during nighttime, EST shows dependence upon the F-layer peak height (hmF2), it shows by day a dependence on electron temperature.
BibTeX:
@article{Pandey2001,
  author = {V.K. Pandey and N.K. Sethi and K.K. Mahajan},
  title = {Equivalent slab thickness and its variability: a study with incoherent scatter measurements},
  journal = {Advances in Space Research },
  year = {2001},
  volume = {27},
  number = {1},
  pages = {60-64},
  url = {http://www.sciencedirect.com/science/article/pii/S027311770000140X},
  doi = {10.1016/S0273-1177(00)00140-X}
}
Peria WJ and Kelley MC (2001), "Convection electric field observations near the Arecibo HF heater beam", Journal of Geophysical Research: Space Physics. Vol. 106(A9), pp. 18517-18524.
Abstract: Electric fields have been observed at the westward edge of the Arecibo HF heater beam, at the F region reflection altitude, by a sounding rocket. We first show that the floating double probe used for these measurements is functioning reliably. The data are shown to be free of sheath rectification effects within the heated volume. Away from the heater beam the double probe data show primarily motional emf, consistent with Earth frame fields of less than 2 m V m-1 (typical, on average, of summer post-midnight conditions over Arecibo), while near the heater beam, significant Earth frame fields are observed. The convective drift due to these fields is consistent with the apparent drift of simultaneously measured heater-induced field-aligned irregularities. The measured convection electric field magnitude is used to estimate the strength of the current maintaining it against the background conductivity, yielding 5 mA m-1. Estimates of the current due to ponderomotive force are lower than this value, unless one invokes electrostatic waves with electric fields roughly 8 times that of the pump field. Temperature gradient currents are estimated as well and are a possible source. The observed shear in the convection electric field is used to estimate a field-aligned current density of 0.5 uA m-2. We conclude that the heater is indeed driving convection on the scale size of the heated volume but are unable to definitively determine how the corresponding electric fields are being produced.
BibTeX:
@article{Peria2001,
  author = {Peria, W. J. and Kelley, M. C.},
  title = {Convection electric field observations near the Arecibo HF heater beam},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2001},
  volume = {106},
  number = {A9},
  pages = {18517-18524},
  url = {http://dx.doi.org/10.1029/2000JA000279},
  doi = {10.1029/2000JA000279}
}
Sasi MN and Vijayan L (2001), "Turbulence characteristics in the tropical mesosphere as obtained by MST radar at Gadanki (13.5� N, 79.2� E)", Annales Geophysicae. Vol. 19(8), pp. 1019-1025.
Abstract: Turbulent kinetic energy dissipation rates (?) and eddy diffusion coefficients (Kz) in the tropical mesosphere over Gadanki (13.5° N, 79.2° E), estimated from Doppler widths of MST radar echoes (vertical beam), observed over a 3-year period, show a seasonal variation with a dominant summer maximum. The observed seasonal variation of ? and Kz in the mesosphere is only partially consistent with that of gravity wave activity inferred from mesospheric winds and temperatures measured by rockets for a period of 9 years at Trivandrum (8.5° N, 77° E) (which shows two equinox and one summer maxima) lying close to Gadanki. The summer maximum of mesospheric ? and Kz values appears to be related to the enhanced gravity wave activity over the low-latitude Indian subcontinent during the southwest monsoon period (June – September). Both ? and Kz in the mesosphere over Gadanki show an increase with an increase in height during all seasons. The absolute values of observed ? and Kz in the mesosphere (above ~80 km) does not show significant differences from those reported for high latitudes. Comparison of observed Kz values during the winter above Gadanki with those over Arecibo (18.5° N, 66° W) shows that they are not significantly different from each other above the ~80 km altitude.
BibTeX:
@article{Sasi2001,
  author = {Sasi, M. N. and Vijayan, L.},
  title = {Turbulence characteristics in the tropical mesosphere as obtained by MST radar at Gadanki (13.5� N, 79.2� E)},
  journal = {Annales Geophysicae},
  year = {2001},
  volume = {19},
  number = {8},
  pages = {1019-1025},
  url = {www.ann-geophys.net/19/1019/2001/},
  doi = {10.5194/angeo-19-1019-2001}
}
Sethi NK and Pandey VK (2001), "Comparative study of electron density from Incoherent scatter measurements at Arecibo with the IRI-95 model during solar maximum", Annales Geophysicae. Vol. 18, pp. 1630-1634.
Abstract: Arecibo (18.4 N, 66.7 W) incoherent scatter (IS) observations of electron density N(h) are compared with the International Reference Ionosphere (IRI-95) during midday (10–14 h), for summer, winter and equinox, at solar maximum (1981). The N(h) profiles below the F2 peak, are normalized to the peak density NmF2 of the F region and are then compared with the IRI-95 model using both the standard B0 (old option) and the Gulyaeva-B0 thickness (new option). The thickness parameter B0 is obtained from the observed electron density profiles and compared with those obtained from the IRI-95 using both the options. Our studies indicate that during summer and equinox, in general, the values of electron densities at all the heights given by the IRI model (new option), are generally larger than those obtained from IS measurements. However, during winter, the agreement between the IRI and the observed values is reasonably good in the bottom part of the F2 layer but IRI underestimates electron density at F1 layer heights. The IRI profiles obtained with the old option gives much better results than those generated with the new option. Compared to the observations, the IRI profiles are found to be much thicker using Gulyaeva-B0 option than using standard B0.
BibTeX:
@article{Sethi2001,
  author = {Sethi, N K and Pandey, V K},
  title = {Comparative study of electron density from Incoherent scatter measurements at Arecibo with the IRI-95 model during solar maximum},
  journal = {Annales Geophysicae},
  year = {2001},
  volume = {18},
  pages = {1630-1634},
  url = {http://www.ann-geophys.net/18/1630/2000/},
  doi = {10.1007/s00585-001-1630-0}
}
Sethi N, Pandey V and Mahajan K (2001), "Comparative study of TEC with IRI model for solar minimum period at low latitude", Advances in Space Research. Vol. 27(1), pp. 45-48.
BibTeX:
@article{Sethi2001a,
  author = {N.K. Sethi and V.K. Pandey and K.K. Mahajan},
  title = {Comparative study of TEC with IRI model for solar minimum period at low latitude},
  journal = {Advances in Space Research},
  year = {2001},
  volume = {27},
  number = {1},
  pages = {45-48},
  doi = {10.1016/S0273-1177(00)00139-3}
}
Sojka JJ, Thompson DC, Schunk RW, Bullett TW and Makela JJ (2001), "Assimilation Ionosphere Model: Development and testing with Combined Ionospheric Campaign Caribbean measurements", Radio Science. Vol. 36(2), pp. 247-259.
Abstract: Assimilation Ionosphere Model (AIM) is a physics-based, global, ionospheric specification model that is currently under development. It assimilates a diverse set of real-time (or near-real-time) measurements, such as ionograms, GPS slant total electron content (TEC), and in situ plasma measurements. This study focuses on a middle latitude ionosonde assimilation capability in both local and regional forms. The models described are capable of using theƒ0F2 and hmF2 from ionograms to generate either a local or a regional distribution of the induced plasma drift. This induced drift is usually caused by the meridional neutral wind. Results from a local model (AIM1.03L) and a regional model (AIM1.03R) are presented and compared with the international reference ionosphere (IRI) climatological predictions as well as GPS slant TEC measurements. Results from year-long studies during solar maximum show that the accuracy of the AIM1.03L model is about a factor of 2 better than that of IRI. An initial month-long regional study is also presented, and the results are almost as good. A study is also carried out using observations taken during the Combined Ionospheric Campaign (CIC) held in November, 1997, in the Caribbean. The digisonde located at Ramey Solar Observatory is used to drive the AIM1.03L model, and the predicted GPS slant TECs are compared to those observed by a GPS receiver located at St. Croix. This study confirms that this first step in preparing a weather-sensitive ionospheric representation is superior to a climatological representation. This sets the stage for the development of full assimilation of GPS TEC, in situ density measurements, etc., and it is anticipated that the AIM1.03L-R ionospheric representation will provide an accurate ionospheric specification.
BibTeX:
@article{Sojka2001,
  author = {Sojka, J. J. and Thompson, D. C. and Schunk, R. W. and Bullett, T. W. and Makela, J. J.},
  title = {Assimilation Ionosphere Model: Development and testing with Combined Ionospheric Campaign Caribbean measurements},
  journal = {Radio Science},
  year = {2001},
  volume = {36},
  number = {2},
  pages = {247-259},
  url = {http://dx.doi.org/10.1029/1999RS002411},
  doi = {10.1029/1999RS002411}
}
Thonnard SE and McCoy RP (2001), "Overview of the 1998 Caribbean Ionospheric Campaign", Radio Science. Vol. 36(5), pp. 1199-1207.
Abstract: The Office of Naval Research and the Naval Research Laboratory have coordinated the first of a series of scientific campaigns to gather ionospheric measurements to characterize the dynamics of space weather. The campaign participants include several universities, government agencies, and private corporations. The focus of the campaign is to gather high-quality, spatial and temporal coincident data to study midlatitude ionospheric specification, compare various ionospheric measurement techniques, and lay the groundwork for validating new ionospheric monitoring instruments and models. The location of the campaign was chosen to further investigate midlatitude ionospheric depletions previously observed above Puerto Rico. In addition to direct comparisons an ionospheric specification model currently under construction will assimilate the data set collected during these campaigns. This paper presents an overview of the first campaign that occurred in the Caribbean, centered about Puerto Rico, in June 1998. The paper also includes a brief description of the variety of monitoring techniques used and the preliminary results of the comparison.
BibTeX:
@article{Thonnard2001,
  author = {Thonnard, S. E. and McCoy, R. P.},
  title = {Overview of the 1998 Caribbean Ionospheric Campaign},
  journal = {Radio Science},
  year = {2001},
  volume = {36},
  number = {5},
  pages = {1199-1207},
  url = {http://dx.doi.org/10.1029/2000RS002431},
  doi = {10.1029/2000RS002431}
}
Zhou Q and Mathews J (2001), "Comments on “Modelling the peak of the ionospheric E-layer” by J.E. Titheridge ", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 63(6), pp. 627 - 629.
BibTeX:
@article{Zhou2001627,
  author = {Q.H. Zhou and J.D. Mathews},
  title = {Comments on “Modelling the peak of the ionospheric E-layer” by J.E. Titheridge },
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {2001},
  volume = {63},
  number = {6},
  pages = {627 - 629},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682600002546},
  doi = {10.1016/S1364-6826(00)00254-6}
}
Aponte N, Gonzalez SA, Kelley MC, Tepley CA, Pi X and Iijima B (2000), "Advection of the equatorial anomaly over Arecibo by small-storm related disturbance dynamo electric fields", Geophysical Research Letters. Vol. 27(18), pp. 2833-2836.
Abstract: During highly disturbed geomagnetic periods, both the Arecibo radar and the Ramey ionosonde have recorded impressive nighttime ionospheric enhancements in which the peak electron density exceeded 1 × 1012 m?3 and the F2 peak height went above 400 km. In the past it has been suggested that these events could be caused by either a downward plasmaspheric flux that increases the density in the F region or by an eastward electric field that pushes the equatorial anomaly poleward to the Caribbean sector. On February 17–18, 1999 the Arecibo radar made observations during an event in which the electron density again rose to daytime values near midnight. For this event, the peaks in density were observed predominantly southeast of Arecibo while the ions sustained a northward-eastward motion due to an eastward-southward storm dynamo electric field. TEC maps from GPS for this night confirmed that the density enhancements were due to a poleward expansion of the equatorial anomaly.
BibTeX:
@article{Aponte2000,
  author = {Aponte, Néstor and Gonzalez, Sixto A. and Kelley, Michael C. and Tepley, Craig A. and Pi, Xiaoqing and Iijima, Byron},
  title = {Advection of the equatorial anomaly over Arecibo by small-storm related disturbance dynamo electric fields},
  journal = {Geophysical Research Letters},
  year = {2000},
  volume = {27},
  number = {18},
  pages = {2833-2836},
  url = {http://dx.doi.org/10.1029/2000GL000025},
  doi = {10.1029/2000GL000025}
}
Bishop RL, Earle GD, Herrero FA and Bateman TT (2000), "Observations of an intermediate layer during the Coqui II campaign", Journal of Geophysical Research: Space Physics. Vol. 105(A11), pp. 24963-24971.
Abstract: NASA sounding rocket 21.114, launched March 7, 1998, during the Coqui II campaign, provided neutral wind and plasma density measurements of a weak intermediate layer. The layer was centered near 140 km and had an approximate peak plasma density of 2200 cm-3. The measured winds were typically less than 40 m s-1, in agreement with wind shear formation theory and coincident density observations. The data obtained during the flight allow us to explore the plasma density structure and wind field morphology of the intermediate layer. Coupled with simultaneous data from Arecibo Observatory, the upleg and downleg density profiles provide three spatially separated measurements that enable the first detailed investigation of the horizontal extent and variation of an intermediate layer.
BibTeX:
@article{Bishop2000,
  author = {Bishop, R. L. and Earle, G. D. and Herrero, F. A. and Bateman, T. T.},
  title = {Observations of an intermediate layer during the Coqui II campaign},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2000},
  volume = {105},
  number = {A11},
  pages = {24963-24971},
  url = {http://dx.doi.org/10.1029/1999JA000453},
  doi = {10.1029/1999JA000453}
}
Bust GS, Coco D and Makela JJ (2000), "Combined Ionospheric Campaign 1: Ionospheric tomography and GPS total electron count (TEC) depletions", Geophysical Research Letters. Vol. 27(18), pp. 2849-2852.
Abstract: Results from the June 1998 combined ionospheric campaign (CIC) are presented. The CIC represents an attempt to focus a large number of different instruments on one interesting geophysical region. The Center for Ionospheric Research (CIR) at Applied Research Laboratories, the University of Texas at Austin (ARL:UT), has had several computerized ionospheric tomography (CIT) receivers deployed in the Caribbean region since July 1997. In this paper we compare CIT data, GPS TEC data and data from the incoherent scatter radar at Arecibo to try to obtain an understanding of the temporal and spatial distribution of ionospheric structure observed during the campaign. We use the three data sets as inputs to the 3DVAR tomography algorithm developed at CIR and present results of the 3DVAR “objectively analyzed” electron density field. An ionization wall was found near 40° latitude in agreement with previous Millstone Hill and DMSP observations in high Kp. Several elongated density depletions were also detected.
BibTeX:
@article{Bust2000,
  author = {Bust, Gary S. and Coco, David and Makela, Jonathan J.},
  title = {Combined Ionospheric Campaign 1: Ionospheric tomography and GPS total electron count (TEC) depletions},
  journal = {Geophysical Research Letters},
  year = {2000},
  volume = {27},
  number = {18},
  pages = {2849-2852},
  url = {http://dx.doi.org/10.1029/2000GL000053},
  doi = {10.1029/2000GL000053}
}
Cheung PY, Sulzer MP, DuBois DF and Russell DA (2000), "High-power high-frequency-induced Langmuir turbulence in the smooth ionosphere at Arecibo. II. Low duty cycle, altitude-resolved, observations", Physics of Plasmas. Vol. 8, pp. 802-812.
Abstract: This is the second of two papers comprising a theoretical and observational study of new, altitude-resolved, observations at Arecibo of Langmuir turbulence induced in the ionosphere by a new, more powerful, high frequency heater operated at very low duty cycles. Altitude resolution of 150 m in incoherent scatter radar spectra is made possible by the coded-long-pulse method. Here we present the first observation at Arecibo of the well-developed parametric decay instability and the Langmuir decay instability cascade features in the Thomson scatter radar power spectrum, of the plasma line, at the unmodified matching altitudes under near-cold start conditions. The dependence of the plasma line spectra on altitude, pump power, and density scale length have been studied. The temporal growth and saturation of the spectra during heating and the decay of the spectra in the afterglow of heating has also been studied in detail. Comparisons are made here with the theoretical predictions of the companion paper I [DuBois et al., Phys. Plasmas 8, 791 (2001)]. From these comparisons and a comparison with recent observations at both Arecibo and Tromsø, we conclude that all the predictions of modern Langmuir turbulence theory for the radar spectral signatures of the turbulence in a smooth ionosphere have now been verified
BibTeX:
@article{Cheung2000,
  author = {P. Y. Cheung and M. P. Sulzer and D. F. DuBois and D. A. Russell},
  title = {High-power high-frequency-induced Langmuir turbulence in the smooth ionosphere at Arecibo. II. Low duty cycle, altitude-resolved, observations},
  journal = {Physics of Plasmas},
  year = {2000},
  volume = {8},
  pages = {802-812},
  url = {http://dx.doi.org/10.1063/1.1345704},
  doi = {10.1063/1.1345704}
}
DuBois DF, Russell DA, Cheung PY and Sulzer MP (2000), "High-power high-frequency-induced Langmuir turbulence in the smooth ionosphere at Arecibo. I. Theoretical predictions for altitude-resolved plasma line radar spectra", Physics of Plasmas. Vol. 8, pp. 791-801.
Abstract: This is the first of two papers comprising a theoretical and observational study of new, altitude-resolved, observations at Arecibo of Langmuir turbulence induced in the ionosphere by a powerful high-frequency (hf) heater operated at very low duty cycles. As shown in paper II [Cheung et al., Phys. Plasmas 8, 802 (2001)], higher power enabled the first observation at Arecibo of the well-developed decay-cascade features in the Thomson scatter radar power spectrum at the unmodified matching altitudes. New theoretical predictions are presented here for the parameters of these observations emphasizing the altitude and pump power dependence of the radar spectra and the time dependence of the spectra from the decaying spectra following heater switch-off. Further details of the strong turbulence signatures from higher altitudes are also presented. At the lower matching altitudes the increase, with hf power, of the angular width of the well-developed decay-cascade spectrum allows these spectral features to come into the view of the Arecibo radar. The favorable comparison of the simulation predictions and observations is discussed in the second paper
BibTeX:
@article{DuBois2000,
  author = {D. F. DuBois and D. A. Russell and P. Y. Cheung and M. P. Sulzer},
  title = {High-power high-frequency-induced Langmuir turbulence in the smooth ionosphere at Arecibo. I. Theoretical predictions for altitude-resolved plasma line radar spectra},
  journal = {Physics of Plasmas},
  year = {2000},
  volume = {8},
  pages = {791-801},
  url = {http://dx.doi.org/10.1063/1.1345703},
  doi = {10.1063/1.1345703}
}
Earle GD, Bishop RL, Collins SC, Gonzalez SA and Sulzer MP (2000), "Descending layer variability over Arecibo", Journal of Geophysical Research: Space Physics. Vol. 105(A11), pp. 24951-24961.
Abstract: Descending layers of ionization over Arecibo exhibit very diverse behavior from night to night that does not appear to be strongly correlated to geomagnetic activity, solar forcing, or average semidiurnal tidal winds. On some nights, three or more distinct layers are observed to form near 170 km over timescales of ~2 hours. Rather than descending smoothly over periods of several hours, these layers stall, abruptly disappear, or even reverse direction in the midst of their descent. The time scales for their disappearance are examined and compared to loss rates arising from diffusion and recombination. Diffusion alone is found to be too slow to account for the observations, but recombination is fast enough provided that the convergent wind shear that forms the layer is relatively weak coincident with their disappearance. The continuity equation is solved in conjunction with a time sequence of radar profiles to estimate the vertical drift and horizontal neutral wind consistent with the observed behavior. The resultant wind field is northward, has an average speed of ~80 m s-1, and varies significantly near the altitude where the layers are observed. These inferred winds are consistent with the presence of the observed layers, and their magnitudes as obtained from the classical continuity and momentum equations are reasonable for this altitude range.
BibTeX:
@article{Earle2000,
  author = {Earle, G. D. and Bishop, R. L. and Collins, S. C. and Gonzalez, S. A. and Sulzer, M. P.},
  title = {Descending layer variability over Arecibo},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2000},
  volume = {105},
  number = {A11},
  pages = {24951-24961},
  url = {http://dx.doi.org/10.1029/2000JA000029},
  doi = {10.1029/2000JA000029}
}
Earle GD, Kane TJ, Pfaff RF and Bounds SR (2000), "Ion layer separation and equilibrium zonal winds in midlatitude sporadic E", Geophysical Research Letters. Vol. 27(4), pp. 461-464.
Abstract: In-situ observations of a moderately strong midlatitude sporadic-E layer show a separation in altitude between distinct sublayers composed of Fe+, Mg+, and NO+. From these observations it is possible to estimate the zonal wind field consistent with diffusive equilibrium near the altitude of the layer. The amplitude of the zonal wind necessary to sustain the layer against diffusive effects is less than 10 m/s, and the vertical wavelength is less than 10 km.
BibTeX:
@article{Earle2000a,
  author = {Earle, G. D. and Kane, T. J. and Pfaff, R. F. and Bounds, S. R.},
  title = {Ion layer separation and equilibrium zonal winds in midlatitude sporadic E},
  journal = {Geophysical Research Letters},
  year = {2000},
  volume = {27},
  number = {4},
  pages = {461-464},
  url = {http://dx.doi.org/10.1029/1999GL900572},
  doi = {10.1029/1999GL900572}
}
Friedman JS, Gonzalez SA, Tepley CA, Zhou Q, Sulzer MP, Collins SC and Grime BW (2000), "Simultaneous atomic and ion layer enhancements observed in the mesopause region over Arecibo during the Coqui II Sounding Rocket Campaign", Geophysical Research Letters. Vol. 27(4), pp. 449-452.
Abstract: The NASA Coqui II sounding rocket campaign in Puerto Rico provided the opportunity to obtain a large number of lidar and incoherent scatter radar observations of atomic sodium and ion layers in the upper mesosphere and lower thermosphere. Sodium layer enhancements, coupled with ion layers, were frequently observed in the range of 90–105 km altitude. We found that above 97 km all of the enhanced Na layers were observed to have an associated ion layer, and below that altitude some Na enhancements could occur in their absence. Finally, we show one extraordinary case of a sporadic Na layer that grew to near its peak concentration before the associated ion layer appeared at its altitude.
BibTeX:
@article{Friedman2000,
  author = {Friedman, J. S. and Gonzalez, S. A. and Tepley, C. A. and Zhou, Q. and Sulzer, M. P. and Collins, S. C. and Grime, B. W.},
  title = {Simultaneous atomic and ion layer enhancements observed in the mesopause region over Arecibo during the Coqui II Sounding Rocket Campaign},
  journal = {Geophysical Research Letters},
  year = {2000},
  volume = {27},
  number = {4},
  pages = {449-452},
  url = {http://dx.doi.org/10.1029/1999GL900605},
  doi = {10.1029/1999GL900605}
}
Garcia FJ, Kelley MC, Makela JJ and Huang C-S (2000), "Airglow observations of mesoscale low-velocity traveling ionospheric disturbances at midlatitudes", Journal of Geophysical Research: Space Physics. Vol. 105(A8), pp. 18407-18415.
Abstract: This paper presents a summary of 630.0 nm emission observations made by the Cornell All-Sky Imager that have revealed an abundance of structure in the midlatitude thermosphère. Some events were so bright that the weaker 557.7 nm thermospheric line was readily visible and produced sharper images because of the shorter excitation lifetime. Global Positioning System observations show that the airglow features are traveling ionospheric disturbances (TIDs). The remarkable feature of the data is the overwhelming tendency for these low-velocity TIDs to develop with a northwest to southeast orientation and to propagate in the southwest direction. Speeds ranged from 50 to 170 m/s, and wavelengths ranged from 50 to 500 km. The Perkins instability is investigated as a possible explanation for the structures. The linear theory, including both winds and electric fields, predicts a positive but small growth rate. However, the real part of the dispersion relation gives the wrong sign for the wave propagation. Furthermore, the growth rate seems too small to amplify a seed gravity wave significantly during one period of neutral gas oscillation. We conclude that this class of low-velocity TID is not yet explained theoretically.
BibTeX:
@article{Garcia2000,
  author = {Garcia, F. J. and Kelley, M. C. and Makela, J. J. and Huang, C.-S.},
  title = {Airglow observations of mesoscale low-velocity traveling ionospheric disturbances at midlatitudes},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2000},
  volume = {105},
  number = {A8},
  pages = {18407-18415},
  url = {http://dx.doi.org/10.1029/1999JA000305},
  doi = {10.1029/1999JA000305}
}
Garcia FJ, Kelley MC, Makela JJ, Sultan PJ, Pi X and Musman S (2000), "Mesoscale structure of the midlatitude ionosphere during high geomagnetic activity: Airglow and GPS observations", Journal of Geophysical Research: Space Physics. Vol. 105(A8), pp. 18417-18427.
Abstract: On the night of November 22, 1997, the Cornell All-Sky Imager recorded a spectacular display of structure in the 630.0 nm emission over Arecibo, Puerto Rico. This event is an example of a phenomenon we have termed “intense midlatitude spread F.” In this paper we describe the stormtime geophysical conditions for the period and detail the evolution of the event. The daytime midlatitude ionosphere was disturbed for four consecutive days. The initial daytime doubling of the total electron content (TEC) was associated with equatorward propagation of a high-TEC patch that seemed to have associated composition changes. The following days had distinct diurnal double maxima (DDM). The TEC in the Caribbean was very high during the first night of the storm and was extremely structured. Airglow depletions and enhancements surged poleward, bifurcating numerous times in the process. The airglow depletions were collocated with TEC minima along similar lines of sight to Global Positioning System satellites. Eventually, four parallel and very similar airglow wave packets were visible and oriented at an angle similar to the less violent structures reported in the companion paper [Garcia et al., this issue] and moving slowly toward the southwest. We explore a number of possible explanations for these features. We are most confident that secondary instabilities of the generalized ExB process can explain the evolution of the structures once they are formed. The initial process itself remains controversial.
BibTeX:
@article{Garcia2000a,
  author = {Garcia, F. J. and Kelley, M. C. and Makela, J. J. and Sultan, P. J. and Pi, X. and Musman, S.},
  title = {Mesoscale structure of the midlatitude ionosphere during high geomagnetic activity: Airglow and GPS observations},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2000},
  volume = {105},
  number = {A8},
  pages = {18417-18427},
  url = {http://dx.doi.org/10.1029/1999JA000306},
  doi = {10.1029/1999JA000306}
}
Hecht JH, Collins S, Kruschwitz C, Kelley MC, Roble RG and Walterscheid RL (2000), "The excitation of the Na airglow from Coqui Dos rocket and ground-based observations", Geophysical Research Letters. Vol. 27(4), pp. 453-456.
Abstract: On February 20 1998 two rockets were launched from Puerto Rico as part of the Coqui Dos campaign. Data from on-board photometers and ground-based data from a Na lidar and an airglow imager allowed an estimate to be made, using both the TIME-GCM and MSIS models, of the branching coefficient alpha for the Na airglow emission. Assuming the hydrogen density is within the range predicted by the two models the data are consistent with alpha being less than 0.05. This value is well below a recent theoretical estimate of 0.67 and also below the nominally accepted value of 0.1 derived from previous aeronomic data.
BibTeX:
@article{Hecht2000,
  author = {Hecht, J. H. and Collins, S. and Kruschwitz, C. and Kelley, M. C. and Roble, R. G. and Walterscheid, R. L.},
  title = {The excitation of the Na airglow from Coqui Dos rocket and ground-based observations},
  journal = {Geophysical Research Letters},
  year = {2000},
  volume = {27},
  number = {4},
  pages = {453-456},
  url = {http://dx.doi.org/10.1029/1999GL010853},
  doi = {10.1029/1999GL010853}
}
Isham B, Tepley CA, Sulzer MP, Zhou QH, Kelley MC, Friedman JS and Gonzalez SA (2000), "Upper atmospheric observations at the Arecibo Observatory: Examples obtained using new capabilities", Journal of Geophysical Research. Vol. 105({A8}), pp. 18609-18637.
Abstract: The Arecibo Observatory will soon complete a major instrumental upgrade which will provide improved capabilities for observations of the upper atmosphere. As in the past, Arecibo capabilities center on 430-MHz incoherent scatter radar (ISR) measurements of the ionosphere made locally or in conjunction with other national and international incoherent scatter facilities; the upgrade will add the capability for simultaneous two beam incoherent scatter observations and will extend plasma line measurements to ±15 MHz. Aeronomical studies may also be performed using a 46.8-MHz coherent scatter radar, the feed of which is coaxial with the 430-MHz line feed, the newly refurbished medium-frequency (MF) radar facility, and a new digital ionosonde. The original airglow laboratory continues to house the Fabry-Perot interferometers, Ebert-Fastie spectrometer, and tilting filter photometers used for observations of mesospheric, thermospheric, and exospheric airglow, while a new laboratory provides a permanent home for the lidars used for resonance fluorescence observations of atomic metal layers in the mesopause region and for Doppler Rayleigh measurements of the upper stratosphere and lower mesosphere. Finally, the recently upgraded high-frequency, high-power transmitter facility has performed active aeronomical and plasma physical studies alone and in conjunction with other Arecibo and visitor-supplied instruments. Observations performed as the upgrade nears completion have already provided a first look at what lies ahead in areas as diverse and fundamental as the structure and dynamics of the turbopause, the properties of upper atmospheric tides, the electrodynamics of the E and F regions, the dynamics of light ions in the topside, and the physics of plasma turbulence. Examples of these and other observations are presented, and the opportunities for future investigations are discussed.
BibTeX:
@article{Isham2000,
  author = {B. Isham and C. A. Tepley and M. P. Sulzer and Q. H. Zhou and M. C. Kelley and J. S. Friedman and S. A. Gonzalez},
  title = {Upper atmospheric observations at the Arecibo Observatory: Examples obtained using new capabilities},
  journal = {Journal of Geophysical Research},
  year = {2000},
  volume = {105},
  number = {A8},
  pages = {18609-18637},
  url = {http://dx.doi.org/10.1029/1999JA900315},
  doi = {10.1029/1999JA900315}
}
Janches D, Mathews JD, Meisel DD and Zhou Q-H (2000), "Micrometeor Observations Using the Arecibo 430 MHz Radar: I. Determination of the Ballistic Parameter from Measured Doppler Velocity and Deceleration Results", Icarus. Vol. 145, pp. 53-63. Elsevier Science.
Abstract: We present a sample of radar meteors detected during the November 1997 Leonids shower period using the narrow-beam, high-power Arecibo Observatory 430-MHz radar. During this period ~7700 events were detected over 73 h of observations that included six mornings. Near apex-crossing, 6–10 events per minute were observed in the ~300-m diameter beam. From these events a total of 390 meteors are characterized by a clear linear deceleration as derived from the radial Doppler speed determined from the meteor-echo leading-edge (head-echo). We interpret our results in terms of the meteor ballistic parameter—the ratio of the meteoroid mass to cross-sectional area—yielding a physical characterization of these particles prior to any assumptions regarding meteoroid shape and mass density. In addition, we compare these measurements with the results of a numerical solution of the meteor deceleration equation and find them in good agreement. The size and dynamical mass of the meteoroids are estimated considering these particles to be spheres with densities of 3 g/cm3. We also discuss atmospheric energy-loss mechanisms of these meteroids. We believe these are the first radar meteor decelerations detected since those ones reported by J. V. Evans (1966, J. Geophys. Res. 71, 171–188) and F. Verniani (1966, J. Geophys. Res. 71, 2749–2761; 1973, J. Geophys. Res. 78, 8429–8462) and the first ones for meteors of this size.
BibTeX:
@article{Janches2000,
  author = {Janches, D. and Mathews, J D and Meisel, D D and Zhou, Q-H},
  title = {Micrometeor Observations Using the Arecibo 430 MHz Radar: I. Determination of the Ballistic Parameter from Measured Doppler Velocity and Deceleration Results},
  journal = {Icarus},
  publisher = {Elsevier Science},
  year = {2000},
  volume = {145},
  pages = {53-63},
  url = {http://dx.doi.org/10.1006/icar.1999.6330},
  doi = {10.1006/icar.1999.6330}
}
Kagan LM, Kelley MC, Garcia F, Bernhardt PA, Djuth FT, Sulzer MP and Tepley CA (2000), "The Structure of Electromagnetic Wave-Induced 557.7-nm Emission Associated with a Sporadic-E Event over Arecibo", Physical Review Letters. Vol. 85, pp. 218-221.
Abstract: We report observations of electromagnetic wave-induced 557.7-nm emission in correspondence with a sporadic low-altitude plasma layer (the sporadic- E layer, Es). We show that the structure of 557.7-nm emission seen for some events results from a transformation of transmitted energy by ionization clouds, compiling the patchy type Es, and presents a projection of the sporadic- E layer structure on the emission altitude. This allows us to propose the first method for visualizing a horizontal structure of sporadic- E layers.
BibTeX:
@article{Kagan2000,
  author = {Kagan, L. M. and Kelley, M. C. and Garcia, F. and Bernhardt, P.~A. and Djuth, F. T. and Sulzer, M. P. and Tepley, C. A.},
  title = {The Structure of Electromagnetic Wave-Induced 557.7-nm Emission Associated with a Sporadic-E Event over Arecibo},
  journal = {Physical Review Letters},
  year = {2000},
  volume = {85},
  pages = {218-221},
  url = {http://link.aps.org/doi/10.1103/PhysRevLett.85.218},
  doi = {10.1103/PhysRevLett.85.218}
}
Kagan LM and Kelley MC (2000), "A thermal mechanism for generation of small-scale irregularities in the ionospheric E region", Journal of Geophysical Research: Space Physics. Vol. 105(A3), pp. 5291-5303.
BibTeX:
@article{Kagan2000a,
  author = {Kagan, L. M. and Kelley, M. C.},
  title = {A thermal mechanism for generation of small-scale irregularities in the ionospheric E region},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2000},
  volume = {105},
  number = {A3},
  pages = {5291-5303},
  doi = {10.1029/1999JA900415}
}
Kelley MC, Makela JJ, Saito A, Aponte N, Sulzer M and Gonzalez SA (2000), "On the electrical structure of airglow depletion/Height layer bands over Arecibo", Geophysical Research Letters. Vol. 27(18), pp. 2837-2840.
Abstract: Using a combination of airglow images and incoherent scatter radar data, we have explored the electrical structure of the airglow depleted, height layer bands over a mid-latitude site. We find a reproducible electrical signature in both components of the electric field in all events studied. The most pronounced feature is a large northward/upward electric field in the heart of the structure. The latter is identical to the radially outward field reported for mid-latitude conjugate electric fields [Saito et al., 1995], found to trace the poleward edge of the equatorial anomaly. We favorably compare the Arecibo drift to a typical satellite event. These electric fields may reflect a nonlinear evolved state of the Perkins instability or some, as yet, unexplained coupling between atmospheric motion and the plasma embedded in it. We show here that the F-region Pedersen conductivity is much lower in these structures than outside and suggest that this is related to a polarization electric field inside the structure.
BibTeX:
@article{Kelley2000,
  author = {Kelley, Michael C. and Makela, Jonathan J. and Saito, Akinori and Aponte, Nestor and Sulzer, Michael and Gonzalez, Sixto A.},
  title = {On the electrical structure of airglow depletion/Height layer bands over Arecibo},
  journal = {Geophysical Research Letters},
  year = {2000},
  volume = {27},
  number = {18},
  pages = {2837-2840},
  url = {http://dx.doi.org/10.1029/2000GL000024},
  doi = {10.1029/2000GL000024}
}
Kelley MC and Gelinas LJ (2000), "Gradient drift instability in midlatitude sporadic E layers: Localization of physical and wavenumber space", Geophysical Research Letters. Vol. 27(4), pp. 457-460.
Abstract: Ionospheric plasmas containing density gradients are subject to a gradient drift instability under the influence of an externally applied electric field or neutral wind. In this paper we present electric field wave data from the Sudden Atom Layers sounding rocket showing a pure gradient drift instability on the topside of a 1 km thick sporadic E layer. An outer scale of 50 m was determined. Considering the local linear growth rate and the mapping of the electric field structures along magnetic field lines, we conclude that structures with scales larger than 50 m perpendicular to the magnetic field map into regions of linear stability where they are damped. The free energy is localized in wavenumber space, yielding peak fluctuating fields of 6 mV/m, corresponding to electron drifts over 190 m/s and a cascade of energy to meter scales.
BibTeX:
@article{Kelley2000a,
  author = {Kelley, M. C. and Gelinas, L. J.},
  title = {Gradient drift instability in midlatitude sporadic E layers: Localization of physical and wavenumber space},
  journal = {Geophysical Research Letters},
  year = {2000},
  volume = {27},
  number = {4},
  pages = {457-460},
  url = {http://dx.doi.org/10.1029/1999GL900604},
  doi = {10.1029/1999GL900604}
}
Kelley MC, Garcia F, Makela J, Fan T, Mak E, Sia C and Alcocer D (2000), "Highly structured tropical airglow and TEC signatures during strong geomagnetic activity", Geophysical Research Letters. Vol. 27(4), pp. 465-468.
Abstract: A remarkable set of all-sky images using the 630 nm airglow emission has been taken over the Arecibo Observatory in Puerto Rico. Wave-like structures at a height of about 250 km are commonly found to travel in the southwest direction at speeds ranging from 20–120 m/s. Most surprising is that geomagnetic activity seems to greatly amplify them, forming very intricate patterns of light and dark. Simultaneous observations using GPS satellite transmissions on one night reveal that dark regions are severely plasma depleted while bright regions have nighttime content as large as the full noontime ionosphere. This unexpected geomagnetic effect at mid-latitudes has implications for trans-ionospheric radiowave propagation and Space Weather.
BibTeX:
@article{Kelley2000b,
  author = {Kelley, M. C. and Garcia, F. and Makela, J. and Fan, T. and Mak, E. and Sia, C. and Alcocer, D.},
  title = {Highly structured tropical airglow and TEC signatures during strong geomagnetic activity},
  journal = {Geophysical Research Letters},
  year = {2000},
  volume = {27},
  number = {4},
  pages = {465-468},
  url = {http://dx.doi.org/10.1029/1999GL900598},
  doi = {10.1029/1999GL900598}
}
Kelley MC, Makela JJ, Swartz WE, Collins SC, Thonnard S, Aponte N and Tepley CA (2000), "Caribbean Ionosphere Campaign, year one: Airglow and plasma observations during two intense mid-latitude spread-F events", Geophysical Research Letters. Vol. 27(18), pp. 2825-2828.
Abstract: A series of campaigns has been carried out in the Caribbean over a one-year period to study intense mid-latitude spread-F events using a cluster of diversified instrumentation. These events are relatively rare but a number of them have now been captured and will be discussed in this and several companion papers. This paper focuses on 630 nm airglow images obtained by the Cornell All-Sky Imager for two of the more spectacular cases that began on February 17, 1998 and February 17, 1999. In the latter case, and for the first time, a poleward surge of depletion/enhancement airglow zones was captured by radar as well as an airglow imager. In the former case structures grew in place overhead and produced strong VHF F-region backscatter as observed by the CUPRI and University of Illinois radars; the other event, exactly one year later, did not result in detectable 3-m backscatter. The two data sets show quantitatively that the low airglow region is elevated in height and depleted in plasma density and Pedersen conductivity. We suggest an enhanced eastward electric field inside the low conductivity zone may be responsible for the surge. The data also suggest small scale turbulence can only be observed in developing structures.
BibTeX:
@article{Kelley2000c,
  author = {Kelley, Michael C. and Makela, Jonathan J. and Swartz, Wesley E. and Collins, Stephen C. and Thonnard, Stefan and Aponte, Nestor and Tepley, Craig A.},
  title = {Caribbean Ionosphere Campaign, year one: Airglow and plasma observations during two intense mid-latitude spread-F events},
  journal = {Geophysical Research Letters},
  year = {2000},
  volume = {27},
  number = {18},
  pages = {2825-2828},
  url = {http://dx.doi.org/10.1029/2000GL000022},
  doi = {10.1029/2000GL000022}
}
Lancaster RS, Waldrop LS, Kerr RB, Noto J, Solomon SC, Tepley CA, Garcia R and Friedman J (2000), "Brightness measurements of the nighttime O I 8446 Å airglow emission from the Millstone Hill and Arecibo Observatories", Journal of Geophysical Research: Space Physics. Vol. 105(A3), pp. 5275-5290.
Abstract: Ground-based measurements of the O I 8446 Å airglow brightness are made from the Millstone Hill and Arecibo Observatories. These measurements are made at various times throughout the year, and this paper reports those made between the years of 1993 and 1996. The maximum brightness of the 8446 Å airglow emission is found to be less than about 35 Rayleighs during the nighttime at both these midlatitude sites. During the summer this emission is present for only a short time in the evening and morning. During the winter the emission can persist throughout the night. This observed behavior is in agreement with the calculations of current models that predict similar intensities from excitation by photoelectron impact on atomic oxygen. A close examination of these data, however, reveal that differences exist between the model predictions and the measured brightness. One difference is a persistence of the nighttime 8446 Å brightness to times when the model predicts little or no emission from photoelectron production. A second difference is an occasional enhancement of the morning 8446 Å brightness that is not predicted by the model. The former of these differences implies a shortcoming in current understanding of the 8446 Å production mechanisms and must be resolved before atomic oxygen can be monitored from the ground using this emission. The latter may have important consequences for our understanding of upper atmosphere dynamics.
BibTeX:
@article{Lancaster2000,
  author = {Lancaster, Redgie S. and Waldrop, Laura S. and Kerr, Robert B. and Noto, John and Solomon, Stanley C. and Tepley, Craig A. and Garcia, Raul and Friedman, Jonathan},
  title = {Brightness measurements of the nighttime O I 8446 Å airglow emission from the Millstone Hill and Arecibo Observatories},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2000},
  volume = {105},
  number = {A3},
  pages = {5275-5290},
  url = {http://dx.doi.org/10.1029/1999JA900410},
  doi = {10.1029/1999JA900410}
}
Larsen MF (2000), "Coqui 2: Mesospheric and lower thermospheric wind observations over Puerto Rico", Geophysical Research Letters. Vol. 27(4), pp. 445-448.
Abstract: During the 1998 Coqui 2 sounding rocket campaign, three chemical release rockets were launched from Puerto Rico to measure the wind profiles in the mesosphere and lower thermosphere region. The first release took place on February 19, and the next two releases were five days later and four hours apart. All three measurements show large winds and wind shears in the altitude range between 95 and 110 km. The largest wind speeds occurred near 100 km with horizontal flow velocities close to 150 m s-1. Taken in isolation, such features may appear to be unusual, but in fact, a large number of earlier rocket measurements show wind features similar to those observed in the Coqui 2 campaign. Such large winds are therefore not an isolated but rather a common feature of the wind profiles at midlatitudes in an altitude range that is critical for the electrodynamics of the ionosphere. The wind profile characteristics described here are not generally well known since the earlier more extensive chemical release data sets were only published in reports with a rather limited distribution.
BibTeX:
@article{Larsen2000,
  author = {Larsen, M. F.},
  title = {Coqui 2: Mesospheric and lower thermospheric wind observations over Puerto Rico},
  journal = {Geophysical Research Letters},
  year = {2000},
  volume = {27},
  number = {4},
  pages = {445-448},
  url = {http://dx.doi.org/10.1029/1999GL010704},
  doi = {10.1029/1999GL010704}
}
MacPherson B, Gonzalez SA, Sulzer MP, Bailey GJ, Djuth F and Rodriguez P (2000), "Measurements of the topside ionosphere over Arecibo during the total solar eclipse of February 26, 1998", Journal of Geophysical Research: Space Physics. Vol. 105(A10), pp. 23055-23067.
Abstract: The Arecibo incoherent scatter radar facility was operated on February 26, 1998, and was used to observe the total solar eclipse that occurred over the Caribbean. A maximum of 87% obscuration was observed over Arecibo at 1430 LT (1830 UT). The radar was operated using an experimental technique, which uses a 300 ?s single/multi-frequency pulse, to gather data from the altitude range 146–2412 km. The Sheffield University plasmasphere ionosphere model was used to interpret the measurements. The electron temperature was found to have decreased by 600 K at 400 km altitude, but the magnitude of the decrease becomes smaller with increasing altitude. This is shown to be the result of the lesser degree of obscuration of the solar disk at latitudes north of Arecibo. Conjugate point photoelectron heating effects are also shown to play a significant role in the electron energy balance during the eclipse. The H+ ion temperature exhibited a response to the eclipse, with temperatures being around 200 K lower than expected at the time of maximum obscuration. There was relatively little variation observed in the O+ temperature. The response of the topside ionosphere is characterized by a downward motion arising from the contraction of the plasma due to reduced plasma temperatures. This is most clearly seen in the O+-H+ transition altitude which falls by 200 km. The transition altitude fully recovers within 2 hours after the eclipse. The location of the transition altitude acts to mitigate the effects of the eclipse on the topside electron densities.
BibTeX:
@article{MacPherson2000,
  author = {MacPherson, B. and Gonzalez, S. A. and Sulzer, M. P. and Bailey, G. J. and Djuth, F. and Rodriguez, P.},
  title = {Measurements of the topside ionosphere over Arecibo during the total solar eclipse of February 26, 1998},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2000},
  volume = {105},
  number = {A10},
  pages = {23055-23067},
  url = {http://dx.doi.org/10.1029/2000JA000145},
  doi = {10.1029/2000JA000145}
}
MacPherson B, Gonzalez SA, Pi X, Kelley M, Bailey GJ, Sulzer MP, Hajj G, Buonsanto M and Wang C (2000), "Comparison between SUPIM simulations and measured TEC for the January, 1997 storm", Geophysical Research Letters. Vol. 27(18), pp. 2845-2848.
Abstract: A method of extrapolating electron densities (Ne) from Incoherent Scatter Radar (ISR) data to high altitudes is presented, and is used to estimate the vertical Total Electron Content (TEC) over Arecibo. Although primarily intended for use on the Ne profiles obtained using the new topside frequency hopping mode at Arecibo which provides measurements to over 2000 km altitude, we show that if the O+ -H+ transition altitude is low enough to be observed, then the method may also be applied to the data taken using the standard World Day multi-radar mode, and thus to a great fraction of the World Day data from low solar flux conditions. This method is applied to Arecibo ISR data taken during the January 6–11 1997 CEDAR storm period, and compared with measured TEC from the Global Positioning System (GPS) satellite network. In addition, the TEC is compared to TEC calculated from the Sheffield University Plasmasphere Ionosphere Model (SUPIM) as part of an ongoing project of model validation.
BibTeX:
@article{MacPherson2000a,
  author = {MacPherson, B. and Gonzalez, S. A. and Pi, X. and Kelley, M. and Bailey, G. J. and Sulzer, M. P. and Hajj, G. and Buonsanto, M. and Wang, C.},
  title = {Comparison between SUPIM simulations and measured TEC for the January, 1997 storm},
  journal = {Geophysical Research Letters},
  year = {2000},
  volume = {27},
  number = {18},
  pages = {2845-2848},
  url = {http://dx.doi.org/10.1029/2000GL000026},
  doi = {10.1029/2000GL000026}
}
Makela JJ, Gonzalez SA, MacPherson B, Pi X, Kelley MC and Sultan PJ (2000), "Intercomparisons of total electron content measurements using the Arecibo Incoherent Scatter Radar and GPS", Geophysical Research Letters. Vol. 27(18), pp. 2841-2844.
Abstract: We compare total electron content measurements made using the Arecibo Incoherent Scatter Radar (ISR) with those made using the Global Positioning System (GPS). The ISR measurements have a limited range for these observations, up to 1500 km. We extend these profiles to GPS heights of 20,200 km with the aid of a numerical model. We use a GPS receiver on St. Croix, which has been calibrated using JPL's Global Ionospheric Mapping (GIM) technique. In addition, we also use the ISR to calibrate GPS measurements made at Isabela, PR and see how the calibration holds up on the next day. The GIM technique gives very good results on both a quiet night and a night with a severe ionospheric depletion. Normalizing the Isabela receiver to the ISR also gives good results and shows promise as a way to independently calibrate nearby GPS receivers in the future. Finally, we give evidence that the severe depletion observed by the ISR on the night of June 25/26, 1998 was associated with an elongated TEC depletion. The structure may be related to a disturbance originating in the southern hemisphere.
BibTeX:
@article{Makela2000,
  author = {Makela, Jonathan J. and Gonzalez, Sixto A. and MacPherson, Bryan and Pi, Xiaoqing and Kelley, Michael C. and Sultan, Peter J.},
  title = {Intercomparisons of total electron content measurements using the Arecibo Incoherent Scatter Radar and GPS},
  journal = {Geophysical Research Letters},
  year = {2000},
  volume = {27},
  number = {18},
  pages = {2841-2844},
  url = {http://dx.doi.org/10.1029/2000GL000023},
  doi = {10.1029/2000GL000023}
}
Pandey VK, Sethi NK and Mahajan KK (2000), "Comparing IRI E-region peak height (hmE) with incoherent scatter data", Advances in Space Research. Vol. 25(1), pp. 65-68.
BibTeX:
@article{Pandey2000,
  author = {Pandey, V K and Sethi, N K and Mahajan, K K},
  title = {Comparing IRI E-region peak height (hmE) with incoherent scatter data},
  journal = {Advances in Space Research},
  year = {2000},
  volume = {25},
  number = {1},
  pages = {65-68},
  doi = {10.1016/S0273-1177(99)00898-4}
}
Pi X, Mendillo M, Hughes WJ, Buonsanto MJ, Sipler DP, Kelly J, Zhou Q, Lu G and Hughes TJ (2000), "Dynamical effects of geomagnetic storms and substorms in the middle-latitude ionosphere: An observational campaign", Journal of Geophysical Research: Space Physics. Vol. 105(A4), pp. 7403-7417.
BibTeX:
@article{Pi2000,
  author = {Pi, Xiaoqing and Mendillo, Michael and Hughes, W. Jeffrey and Buonsanto, Michael J. and Sipler, Dwight P. and Kelly, John and Zhou, Qihou and Lu, Gang and Hughes, Terrence J.},
  title = {Dynamical effects of geomagnetic storms and substorms in the middle-latitude ionosphere: An observational campaign},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {2000},
  volume = {105},
  number = {A4},
  pages = {7403-7417},
  doi = {10.1029/1999JA900460}
}
Raizada S and Sinha HSS (2000), "Some new features of electron density irregularities over SHAR during strong spread F", Annales Geophysicae. Vol. 18(2), pp. 141-151.
Abstract: An RH-560 rocket flight was conducted from Sriharikota rocket range (SHAR) (14°N, 80°E, dip latitude 5.5°N) to study electron density and electric field irregularities during spread F. The rocket was launched at 2130 local time (LT) and it attained an apogee of 348 km. Results of electron density fluctuations are presented here. Two extremely sharp layers of very high electron density were observed at 105 and 130 km. The electron density increase in these layers was by a factor of 50 in a vertical extent of 10 km. Large depletions in electron density were observed around 175 and 238 km. Both sharp layers as well as depletions were observed also during the descent. The presence of sharp layers and depletions during the ascent and the descent of the rocket as well as an order of magnitude less electron density, in 150-300 km region during the descent, indicate the presence of strong large-scale horizontal gradients in the electron density. Some of the valley region irregularities (165-178 km), in the intermediate scale size range, observed during this flight, show spectral peaks at 2 km and can be interpreted in terms of the image striation theory suggested by Vickrey et al. The irregularities at 176 km do not exhibit any peak at kilometer scales and appear to be of new type. The growth rate of intermediate scale size irregularities, produced through generalized Rayleigh Taylor instability, was calculated for the 200-330 km altitude, using observed values of electron density gradients and an assumed vertically downward wind of 20 ms-1. These growth rate calculations suggest that the observed irregularities could be produced by the gradient drift instability.
BibTeX:
@article{Raizada2000,
  author = {Raizada, S. and Sinha, H. S. S.},
  title = {Some new features of electron density irregularities over SHAR during strong spread F},
  journal = {Annales Geophysicae},
  year = {2000},
  volume = {18},
  number = {2},
  pages = {141-151},
  url = {http://www.ann-geophys.net/18/141/2000/},
  doi = {10.1007/s00585-000-0141-8}
}
Sinha HSS and Raizada S (2000), "Some new features of ionospheric plasma depletions over the Indian zone using all sky optical imaging", Earth Planets Space. Vol. 52, pp. 549-559.
Abstract: An all sky optical imaging system was operated from Sriharikota rocket range (SHAR) (14° N, 80° E, 5.5° N dip latitude) during January-March, 1993 to observe ionospheric plasma depletions through 630 nm and 777.4 nm night glow emissions. Strong plasma depletions were observed only on four nights viz., 14, 17, 19 and 21 February, 1993. Except the 17 February, which was a magnetically disturbed day, all the other nights pertained to magnetically quiet period. A number of plasma depletion parameters such as, degree of depletion, east-west extent, tilt with respect to the geomagnetic field, inter-depletion distance, drift velocity and plasma enhancements or brightness patterns were estimated. Some of the important results are: (a) It was found that the east-west extent of plasma depletions varied with the degree of depletion; for the 630 nm images the degree of depletion ranged between 6-9% per 100 km east-west extent and for 777.4 nm images it was 3% per 100 km east-west extent, (b) The average inter-depletion distance (IDD) was in the range of 1500±100 km during the magnetically disturbed period and 740±60 km during quiet periods. This is suggestive of gravity wave modulation of the bottom side of the F-region. While the large scale gravity waves (1500±100 km) of auroral origin could be responsible during magnetically disturbed period, smaller scale gravity waves (740±60 km) having their origin in the lower atmosphere could produce initial perturbation in the bottom side of the F-region, (c) Plasma depletions are observed to have an eastward tilt in the range of 10-15° with respect to the geomagnetic field. It has been suggested here that these tilts are associated with the variation of plasma drift with altitude, (d) plasma depletions are observed to be moving eastwards with drift velocities in the range of 40-190 ms-1, and (e) Strong plasma enhancements or brightness patterns were observed on three nights. The degree of enhancement was by a factor of 1.4-3.8. These enhancements lasted for more than 15 minutes. Although, prima facie, these observations look similar to the transient brightness wave reported by Mendillo et al. (1997a), the high degree of enhancement and an extended duration of more than 15 minutes, observed in the present case, need to be understood.
BibTeX:
@article{Sinha2000,
  author = {H. S. S. Sinha and S. Raizada},
  title = {Some new features of ionospheric plasma depletions over the Indian zone using all sky optical imaging},
  journal = {Earth Planets Space},
  year = {2000},
  volume = {52},
  pages = {549-559},
  url = {http://www.terrapub.co.jp/journals/EPS/abstract/5208/52080549.html}
}
Sinha HSS and Raizada S (2000), "First in situ measurement of electric field fluctuations during strong spread F in the Indian zone", Annales Geophysicae. Vol. 18(5), pp. 523-531.
Abstract: An RH-560 rocket flight was conducted from Sriharikota rocket range (SHAR) (14°N, 80°E, dip 14°N) along with other experiments, as a part of equatorial spread F (ESF) campaign, to study the nature of irregularities in electric field and electron density. The rocket was launched at 2130 local time (LT) and it attained an apogee of 348 km. Results of vertical and horizontal electric field fluctuations are presented here. Scale sizes of electric field fluctuations were measured in the vertical direction only. Strong ESF irregularities were observed in three regions, viz., 160-190 km, 210-257 km and 290-330 km. Some of the valley region vertical electric field irregularities (at 165 km and 168 km), in the intermediate-scale size range, observed during this flight, show spectral peak at kilometer scales and can be interpreted in terms of the image striation theory suggested by Vickrey et al. The irregularities at 176 km do not exhibit any peak at kilometer scales and appear to be of a new type. Scale sizes of vertical electric field fluctuations showed a decrease with increasing altitude. The most prominent scales were of the order of a few kilometers around 170 km and a few hundred meters around 310 km. Spectra of intermediate-scale vertical electric field fluctuations below the base of the F region (210-257 km) showed a tendency to become slightly flatter (spectral index n = -2.1 ± 0.7) as compared to the valley region (n = -3.6 ± 0.8) and the region below the F peak (n = -2.8 ± 0.5). Correlation analysis of the electron density and vertical electric field fluctuations suggests the presence of a sheared flow of current in 160-330 km region.
BibTeX:
@article{Sinha2000a,
  author = {Sinha, H. S. S. and Raizada, S.},
  title = {First in situ measurement of electric field fluctuations during strong spread F in the Indian zone},
  journal = {Annales Geophysicae},
  year = {2000},
  volume = {18},
  number = {5},
  pages = {523-531},
  url = {http://www.ann-geophys.net/18/523/2000/},
  doi = {10.1007/s00585-000-0523-y}
}
Swartz WE, Kelley MC, Makela JJ, Collins SC, Kudeki E, Franke S, Urbina J, Aponte N, Sulzer MP and Gonzalez SA (2000), "Coherent and incoherent scatter radar observations during intense mid-latitude spread F", Geophysical Research Letters. Vol. 27(18), pp. 2829-2832.
BibTeX:
@article{Swartz2000,
  author = {Swartz, Wesley E. and Kelley, Michael C. and Makela, Jonathan J. and Collins, Stephen C. and Kudeki, Erhan and Franke, Steve and Urbina, Julio and Aponte, Nestor and Sulzer, Michael P. and Gonzalez, Sixto A.},
  title = {Coherent and incoherent scatter radar observations during intense mid-latitude spread F},
  journal = {Geophysical Research Letters},
  year = {2000},
  volume = {27},
  number = {18},
  pages = {2829-2832},
  doi = {10.1029/2000GL000021}
}
Swartz WE, Makela JJ and Kelley MC (2000), "First observations of coherent scatter from the mid-latitude F-region in the Caribbean", Geophysical Research Letters. Vol. 27(7), pp. 935-938.
Abstract: The Cornell University Portable Radar Interferometer (CUPRI) started a new series of measurements of the mid-latitude ionosphere from Puerto Rico in July 1997. On the first day of operation, coherent echoes were obtained from the F region. This was the first detection of such echoes in this longitude sector. This is surprising since the MU radar has seen similar eches over Japan and the presence of related phenomena in the Caribbean suggested they should have been seen in other VHF studies. A number of F-region events were subsequently observed. Some echoes were characterized with very narrow spectra and small mean Doppler shifts. Two events had echoes whose range changed rapidly with time, but only one of these had comparable Doppler velocities. Such differences suggest that we caught the events in different stages of development. In addition to presenting samples of the data, we outline the reasons why these structures were anticipated.
BibTeX:
@article{Swartz2000a,
  author = {Swartz, Wesley E. and Makela, Jonathan J. and Kelley, Michael C.},
  title = {First observations of coherent scatter from the mid-latitude F-region in the Caribbean},
  journal = {Geophysical Research Letters},
  year = {2000},
  volume = {27},
  number = {7},
  pages = {935-938},
  url = {http://dx.doi.org/10.1029/1999GL010741},
  doi = {10.1029/1999GL010741}
}
Urbina J, Kudeki E, Franke SJ, Gonzalez S, Zhou Q and Collins SC (2000), "50 MHz radar observations of mid-latitude E-region irregularities at Camp Santiago, Puerto Rico", Geophysical Research Letters. Vol. 27(18), pp. 2853-2856.
Abstract: A 50 MHz radar interferometer was used near Salinas, Puerto Rico, to probe the meter-scale E-region plasma density irregularities during two campaigns conducted in 1998. During the February–April period E-region echoing layers were primarily observed between 90 and 100 km heights. The layers were typically thin (~1 km) and unstructured, although in several cases short period (~90 s) layer oscillations were observed. During the June-July period E-region echoes showed more varied characteristics. In addition to low altitude layers, quasi-periodic structures with descending echoing layers were observed at altitudes above 100 km. Zonal motions detected during descending layer events were at times variable and oscillated between westward and eastward directions while the layer descent rates remained fixed.
BibTeX:
@article{Urbina2000,
  author = {Urbina, Julio and Kudeki, Erhan and Franke, Steven J. and Gonzalez, Sixto and Zhou, Qihou and Collins, Stephen C.},
  title = {50 MHz radar observations of mid-latitude E-region irregularities at Camp Santiago, Puerto Rico},
  journal = {Geophysical Research Letters},
  year = {2000},
  volume = {27},
  number = {18},
  pages = {2853-2856},
  url = {http://dx.doi.org/10.1029/2000GL000028},
  doi = {10.1029/2000GL000028}
}
Walterscheid RL, Hecht JH, Djuth FT and Tepley CA (2000), "Evidence of reflection of a long-period gravity wave in observations of the nightglow over Arecibo on May 8-9, 1989", Journal of Geophysical Research: Atmospheres. Vol. 105(D5), pp. 6927-6934.
Abstract: During the Arecibo Initiative in Dynamics of the Atmosphere (AIDA) campaign there were several unusual observations of the O2 Atmospheric (0,1) and OH Meinel (6,2) brightness fluctuations being nearly 180° out of phase. In this paper we discuss data from May 8–9, 1989, during which meteor radar and airglow instrumentations were operating and thus wind data were available. We show that the nearly out-of-phase result on this night is due to the fact that the OH Meinel brightness and temperature are out of phase while the O2 atmospheric temperature and brightness are nearly in phase. The characteristics of the wave causing the out of phase fluctuations are derived and comparisons are made between results obtained by the Aerospace nightglow camera and those obtained by the York University airglow camera [Zhang et al., 1993]. Although there are differences between them, both of the instrumental data sets are consistent with the presence of a wave with a horizontal wavelength >=600 km and a period of several hours. An analysis of these data shows that the out-of-phase relationship is most likely due to strong wave reflection in the lower thermosphere caused by thermal gradients and wind shears.
BibTeX:
@article{Walterscheid2000,
  author = {Walterscheid, R. L. and Hecht, J. H. and Djuth, F. T. and Tepley, C. A.},
  title = {Evidence of reflection of a long-period gravity wave in observations of the nightglow over Arecibo on May 8-9, 1989},
  journal = {Journal of Geophysical Research: Atmospheres},
  year = {2000},
  volume = {105},
  number = {D5},
  pages = {6927-6934},
  url = {http://dx.doi.org/10.1029/1999JD901065},
  doi = {10.1029/1999JD901065}
}
Aponte N, Swartz WE and Farley DT (1999), "Electron energy balance in the F region above Jicamarca", Journal of Geophysical Research: Space Physics. Vol. 104(A5), pp. 10041-10049.
Abstract: Incoherent scatter measurements from Jicamarca, Peru, show that current models and cross sections account quite well for the heating and cooling of F region electrons, in marked contrast to earlier similar studies at low and middle latitudes. The latter showed discrepancies of the order of a factor of 2 between the calculated energy input and loss rates. The equatorial F region ionosphere provides the simplest configuration for such studies because the horizontal magnetic field eliminates vertical photoelectron transport and thermal conduction. We based our estimates of electron heating on photoelectron energy spectra computed from recently developed solar flux models and new absorption and ionization cross sections and included the additional energy source clue to quenching of the 2D metastable state of nitrogen. This extra source is sometimes significant. Electron and ion temperatures and densities measured with the Jicamarca incoherent scatter radar were used to complete the calculations of the heating and cooling rates. We present here data from 2 days, one with low solar activity and one with moderate activity, over the altitude range 220–325 km. The heating/cooling rates ranged from about 500 to 6000 eV cm-3 s-1. Over this entire range the calculated heating and cooling rates differed by 10% or less when the data quality was good.
BibTeX:
@article{Aponte1999,
  author = {Aponte, Nestor and Swartz, Wesley E. and Farley, Donald T.},
  title = {Electron energy balance in the F region above Jicamarca},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {1999},
  volume = {104},
  number = {A5},
  pages = {10041-10049},
  url = {http://dx.doi.org/10.1029/1999JA900054},
  doi = {10.1029/1999JA900054}
}
Buonsanto M, González S, Pi X, Ruohoniemi J, Sulzer M, Swartz W, Thayer J and Yuan D (1999), "Radar chain study of the May, 1995 storm ", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 61(3–4), pp. 233 - 248.
Abstract: We summarize the main features of the ionospheric F region as observed bythe Sondrestrom, Millstone Hill, Arecibo, and Jicamarca incoherent scatter radars during the 1–5May, 1995 CEDAR Storm Study interval. This paper apparently represents the first study of amajor storm interval using the current incoherent scatter radar chain supported by the U.S.National Science Foundation. We focus most attention on 2–3 May, and include additional datafrom IMP-8, the St. Johns magnetometer, SuperDARN, and global total electron content (TEC)maps from GPS. Three intervals of likely penetration of magnetospheric electric field from high tolow latitude are identified on 2 May. A unique feature of this storm are the strong daytimeequatorward wind surges in the neutral meridional wind observed at Millstone Hill. The first ofthese (at 14 UT on 2 May) is apparently due to a travelling atmospheric disturbance launched byintense frictional and Joule heating as observed at Sondrestrom. An evening enhancement in NmF2 (the dusk effect) is typically seen only on the first day of a geomagneticstorm. However, during this storm a strong dusk effect is seen at Millstone Hill on 2, 3, and 4May, associated with the equatorward wind surges. A penetrating eastward electric field alsocontributed to the dusk effect on 2 May. A large rise in hmF2 at Arecibo near0000 UT on 3 May is due to the same eastward electric field, which penetrates to the equator,causing a strong upward plasma drift at Jicamarca. This apparently results in a polewardexpansion of the equatorial anomaly zones as seen in GPS total electron content, and an increasein NmF2 at Arecibo to the largest value seen at midnight in several years.
BibTeX:
@article{Buonsanto1999233,
  author = {M.J Buonsanto and S.a González and X Pi and J.M Ruohoniemi and M.P Sulzer and W.e Swartz and J.P Thayer and D.N Yuan},
  title = {Radar chain study of the May, 1995 storm },
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {1999},
  volume = {61},
  number = {3–4},
  pages = {233 - 248},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682698001345},
  doi = {10.1016/S1364-6826(98)00134-5}
}
Buonsanto MJ, Gonzalez SA, Lu G, Reinisch BW and Thayer JP (1999), "Coordinated incoherent scatter radar study of the January 1997 storm", Journal of Geophysical Research: Space Physics. Vol. 104(A11), pp. 24625-24637.
BibTeX:
@article{Buonsanto1999a,
  author = {Buonsanto, M. J. and Gonzalez, S. A. and Lu, G. and Reinisch, B. W. and Thayer, J. P.},
  title = {Coordinated incoherent scatter radar study of the January 1997 storm},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {1999},
  volume = {104},
  number = {A11},
  pages = {24625-24637},
  doi = {10.1029/1999JA900358}
}
Buonsanto M (1999), "Ionospheric Storms - A Review", Space Science Reviews. Vol. 88(3-4), pp. 563-601.
BibTeX:
@article{Buonsanto1999b,
  author = {Buonsanto, M.J.},
  title = {Ionospheric Storms - A Review},
  journal = {Space Science Reviews},
  year = {1999},
  volume = {88},
  number = {3-4},
  pages = {563-601},
  doi = {10.1023/A:1005107532631}
}
Carter LN and Forbes JM (1999), "Global transport and localized layering of metallic ions in the upper atmospherere", Annales Geophysicae. Vol. 17(2), pp. 190-209.
BibTeX:
@article{Carter1999,
  author = {Carter, L. N. and Forbes, J. M.},
  title = {Global transport and localized layering of metallic ions in the upper atmospherere},
  journal = {Annales Geophysicae},
  year = {1999},
  volume = {17},
  number = {2},
  pages = {190-209},
  doi = {10.1007/s00585-999-0190-6}
}
Djuth FT, Bernhardt PA, Tepley CA, Gardner JA, Kelley MC, Broadfoot AL, Kagan LM, Sulzer MP, Elder JH, Selcher C, Isham B, Brown C and Carlson HC (1999), "Large airglow enhancements produced via wave-plasma interactions in sporadic E", Geophysical Research Letters. Vol. 26(11), pp. 1557-1560.
BibTeX:
@article{Djuth1999,
  author = {Djuth, F. T. and Bernhardt, P. A. and Tepley, C. A. and Gardner, J. A. and Kelley, M. C. and Broadfoot, A. L. and Kagan, L. M. and Sulzer, M. P. and Elder, J. H. and Selcher, C. and Isham, B. and Brown, C. and Carlson, H. C.},
  title = {Large airglow enhancements produced via wave-plasma interactions in sporadic E},
  journal = {Geophysical Research Letters},
  year = {1999},
  volume = {26},
  number = {11},
  pages = {1557-1560},
  doi = {10.1029/1999GL900296}
}
Franz TL, Kelley MC and Gurevich AV (1999), "Radar backscattering from artificial field-aligned irregularities", Radio Science. Vol. 34(2), pp. 465-475.
Abstract: In June of 1992 a NASA sounding rocket was fired into the Arecibo heater beam to provide in situ observations of artificially induced ionospheric irregularities. In this paper we provide a radar scattering calculation based on in situ data and compare the same with previous remote sensing experiments and with theory. The calculated backscatter cross section is in good agreement with prior observations over the Arecibo heater at 50 MHz. More important, when we scale the observed in situ power spectrum appropriately and compare it with multiradar cross-sectional results from the Platteville, Colorado experiments, we find a remarkably similar radar frequency dependence, albeit one shifted to smaller scales over the higher-latitude site. Even though the rms fluctuation level is almost the same over the Arecibo and Platteville heaters, the shift in scales toward smaller structures over Platteville explains the much larger VHF radar cross section measured there. Comparison of our waveform and its power spectrum with similar predictions from a recent theory shows excellent agreement for k values up to about 5 times the breakpoint in the spectrum of the theoretical prediction. Taken together, these results give very strong evidence for the production of needle-like solitary structures as the dominant final state when high-power radio waves reflect from a magnetized plasma. The organization of these structures by as yet unexplained processes may explain the scales between 10 m and 10 km which occur in the heated volume. Finally, the dominant needle-like field-aligned density depletions seem to support a second source of smaller-scale irregularities. This creates a second break in the power law slope from its one-dimensional value of k-4.3 predicted by theory to one more nearly characterized by k-3. The multiradar results from Platteville show a similar break, and we speculate that a density and/or temperature-gradient-driven instability such as the drift wave is operating.
BibTeX:
@article{Franz1999,
  author = {Franz, T. L. and Kelley, M. C. and Gurevich, A. V.},
  title = {Radar backscattering from artificial field-aligned irregularities},
  journal = {Radio Science},
  year = {1999},
  volume = {34},
  number = {2},
  pages = {465-475},
  url = {http://dx.doi.org/10.1029/1998RS900035},
  doi = {10.1029/1998RS900035}
}
Grime BW, Kane TJ, Collins SC, Kelley MC, Kruschwitz CA, Friedman JS and Tepley CA (1999), "Meteor trail advection and dispersion; Preliminary lidar observations", Geophysical Research Letters. Vol. 26(6), pp. 675-678.
Abstract: Sodium resonance lidar observations of meteor ablation trails at the Arecibo Observatory (18.30°N, 66.75°W) are presented. Of particular interest is the event of 23 March 1998, during the Coqui II sounding rocket campaign. On this date, the lidar was operating with two beams probing different volumes of the sodium layer separated zonally by 15.7±0.8 km. A single meteor trail was observed near 89 km altitude in both lidar field-of-views with a 310±50 s temporal displacement. This observational separation suggested a westward zonal wind of 50±10 m/s, while trail dispersion yielded an upper bound for the total diffusion coefficient of 2.6±0.5 m²/s which is consistent with dispersion seen in other trails. The data supports the need for future observation with systems specialized for meteor detection.
BibTeX:
@article{Grime1999,
  author = {Grime, Brent W. and Kane, Timothy J. and Collins, Stephen C. and Kelley, Michael C. and Kruschwitz, Craig A. and Friedman, Jonathan S. and Tepley, Craig A.},
  title = {Meteor trail advection and dispersion; Preliminary lidar observations},
  journal = {Geophysical Research Letters},
  year = {1999},
  volume = {26},
  number = {6},
  pages = {675-678},
  url = {http://dx.doi.org/10.1029/1999GL900053},
  doi = {10.1029/1999GL900053}
}
Zhou QH, Mathews JD and Zhou QN (1999), "Incoherent Scatter radar study of the impact of the meteoric influx on nocturnal E-region ionization", Geophysical Research Letters. Vol. 26(13), pp. 1833-1836.
Abstract: We use the Arecibo incoherent scatter radar data collected from 1987 to 1995 to study meteoric impact on the nocturnal E-region electron/ion content. The nighttime ionization is observed to increase after midnight, which we interpret to be due to increase in background meteoric input. The column incremental rate due to meteoric ionization between 0100 to 0600 LT is estimated to be 109/cm²/hr. Direct meteoric deposition is responsible for 60% of the total ionization in the morning hours in the altitude range of 97 to 114 km. Although there appears to be an increase in electron content during shower periods, there is not an one-to-one relation between meteor showers and E-region ionization enhancement.
BibTeX:
@article{GRL:GRL13177,
  author = {Zhou, Q. H. and Mathews, J. D. and Zhou, Q. N.},
  title = {Incoherent Scatter radar study of the impact of the meteoric influx on nocturnal E-region ionization},
  journal = {Geophysical Research Letters},
  year = {1999},
  volume = {26},
  number = {13},
  pages = {1833--1836},
  url = {http://dx.doi.org/10.1029/1999GL900369},
  doi = {10.1029/1999GL900369}
}
Gurevich A, Carlson H, Kelley M, Hagfors T, Karashtin A and Zybin K (1999), "Nonlinear Structuring of the Ionosphere Modified by Powerful Radio Waves at Low Latitudes", Physics Letters A. Vol. 251, pp. 311-321.
Abstract: The problem of the nonlinear structuring of the modified ionosphere due to the self-focusing of the pump wave on the bunches of striations is investigated. Two main conditions of self-focusing are formulated: (1) propagation of the pump wave quite along the magnetic field for effective excitation of striations, and (2) trapping of the pump wave by large-scale irregularities. It is shown that both conditions can be easily satisfied for small inclination angles alpha of the magnetic field to the vertical. A detailed study of the low latitude case was performed using model calculations of the pump wave propagation. It is shown that at low latitudes self-focusing conditions also can be satisfied but mostly for the special form of the large-scale irregularities and mostly in the southern part of the pump wave beam. These results may reconcile apparent differences between radiowave and rocket probing of the irregularities.
BibTeX:
@article{Gurevich1999,
  author = {Gurevich, A. and Carlson, H. and Kelley, M. and Hagfors, T. and Karashtin, A. and Zybin, K.},
  title = {Nonlinear Structuring of the Ionosphere Modified by Powerful Radio Waves at Low Latitudes},
  journal = {Physics Letters A},
  year = {1999},
  volume = {251},
  pages = {311-321},
  url = {http://www.sciencedirect.com/science/article/pii/S0375960198007865},
  doi = {10.1016/S0375-9601(98)00786-5}
}
Isham B, La Hoz C, Rietveld MT, Hagfors T and Leyser TB (1999), "Cavitating Langmuir Turbulence Observed during High-Latitude Ionospheric Wave Interaction Experiments", Physical Review Letters., Sep, 1999. Vol. 83, pp. 2576-2579. American Physical Society.
Abstract: Incoherent scatter radar data obtained during high power radio wave ionospheric interaction experiments performed in northern Scandinavia show an induced spectral line at the O-mode pump frequency simultaneous with strong enhancements at the natural Langmuir resonance frequency, both just below the reflection height. These characteristics provide an unmistakable signature of cavitating (a.k.a. strong) Langmuir turbulence, and show that this turbulence occurs not only in midlatitude but also during high latitude ionospheric interaction experiments. Cavitating turbulence is thus not dependent on specific geophysical conditions but is due to fundamental wave-plasma interaction processes in the ionospheric plasma.
BibTeX:
@article{Isham1999,
  author = {Isham, B. and La Hoz, C. and Rietveld, M. T. and Hagfors, T. and Leyser, T. B.},
  title = {Cavitating Langmuir Turbulence Observed during High-Latitude Ionospheric Wave Interaction Experiments},
  journal = {Physical Review Letters},
  publisher = {American Physical Society},
  year = {1999},
  volume = {83},
  pages = {2576-2579},
  url = {http://link.aps.org/doi/10.1103/PhysRevLett.83.2576},
  doi = {10.1103/PhysRevLett.83.2576}
}
Isham B, Rietveld M, Hagfors T, Hoz CL, Mishin E, Kofman W, Leyser T and van Eyken A (1999), "Aspect angle dependence of HF enhanced incoherent backscatter", Advances in Space Research . Vol. 24(8), pp. 1003 - 1006.
Abstract: An HF ionospheric interaction experiment was performed in November and December of 1997 using the EISCAT HF transmitter and 931 and 224 MHz incoherent scatter radars, all co-located near Tromsø, Norway. During this experiment the pointing of the UHF radar was varied in a predetermined and repeating cycle between elevation angles of 90 and 77.2 degrees south, that is, between vertical and geomagnetic field aligned. The HF transmitter duty cycle was intentionally kept to the relatively low value of 2% (200 ms every 10 s) in order to minimize the effects of ionospheric irregularities. Here we report on variations in the intensity of the enhanced incoherent scatter ion and plasma lines observed during the experiment. Bottomside and topside F region enhanced lines were seen with both radars, and while intensity enhancements observed with the UHF radar were clearly correlated with pointing angles between the Spitze angle and field aligned, no correlation between the intensity of the lines observed with the scanning UHF radar and the vertically pointing VHF radar was observed. Consistent with HF propagation theory, the field aligned backscatter observed by the UHF radar originated several kilometers below the HF reflection height.
BibTeX:
@article{Isham19991003,
  author = {B. Isham and M.T. Rietveld and T. Hagfors and C. La Hoz and E. Mishin and W. Kofman and T.B. Leyser and A.P. van Eyken},
  title = {Aspect angle dependence of HF enhanced incoherent backscatter},
  journal = {Advances in Space Research },
  year = {1999},
  volume = {24},
  number = {8},
  pages = {1003 - 1006},
  note = {Active Experiments in Space Plasmas },
  url = {http://www.sciencedirect.com/science/article/pii/S0273117799005554},
  doi = {10.1016/S0273-1177(99)00555-4}
}
Kuo SP and Lee MC (1999), "On the generation of a broad downshifted spectrum of HF wave enhanced plasma lines in the ionospheric heating experiments", Geophysical Research Letters. Vol. 26(21), pp. 3289-3292.
Abstract: Generation of a broad downshifted spectrum of HF wave enhanced plasma Lines (HFPLs) in ionospheric heating experiments is explored. Langmuir waves are first excited within a cone around the geomagnetic field by the HF wave, in the region near its reflection height, through the oscillating two stream instability (OTSI). These Langmuir waves then cascade through a secondary parametric instability, whereby an obliquely propagating Langmuir pump wave decays into an obliquely propagating Langmuir sideband and a lower hybrid decay mode, which propagates in a direction perpendicular to the Langmuir pump wave. The excited Langmuir sidebands have a broad downshifted frequency spectrum and large propagation angles. Their propagation angles are further widened via the filamentation instability or scattering off short-scale field-aligned density irregularities. Thus they become detectable by backscatter radars as HFPLs with a broad downshifted frequency spectrum. The results of our analysis show that it requires HF field amplitude of 3.6 V/m to cascade the OTSI-excited Langmuir waves, for example, 8 times to produce a downshifted spectral width of 50 KHz in the Arecibo heating experiments.
BibTeX:
@article{Kuo1999,
  author = {Kuo, S. P. and Lee, M. C.},
  title = {On the generation of a broad downshifted spectrum of HF wave enhanced plasma lines in the ionospheric heating experiments},
  journal = {Geophysical Research Letters},
  year = {1999},
  volume = {26},
  number = {21},
  pages = {3289-3292},
  url = {http://dx.doi.org/10.1029/1999GL003652},
  doi = {10.1029/1999GL003652}
}
Lee MC, Klien EMC, Burke WJ, Zhang AX, Riddolls RJ, Kuo SP, Sulzer MP and Isham B (1999), "Augmentation of natural ionospheric plasma turbulence by HF heater waves", Geophysical Research Letters. Vol. 26(1), pp. 37-40.
Abstract: HF heating offers a powerful technique for controlled studies of ionospheric plasma turbulence. Heater waves generate large plasma density depletions and sheet-like ionospheric irregularities in the F region, which can give rise to spread F backscatter. Electric fields associated with the induced irregularities can seed plasma instabilities, driven by such environmental causes as density gradients and ambient electric fields, to enhance spread F signatures. Significant reductions in the height-integrated radar backscatter power, measured during the HF heating, indicate the depletion of magnetic flux tubes. Density gradients at the edges of the depletions provide new sources of free energy to augment ionospheric plasma turbulence, enhancing the spread F processes. Furthermore, depleted magnetic flux tubes create and/or alter ionospheric ducts thus affecting radio wave propagation.
BibTeX:
@article{Lee1999,
  author = {Lee, M. C. and Klien, E. M. C. and Burke, W. J. and Zhang, A. X. and Riddolls, R. J. and Kuo, S. P. and Sulzer, M. P. and Isham, B.},
  title = {Augmentation of natural ionospheric plasma turbulence by HF heater waves},
  journal = {Geophysical Research Letters},
  year = {1999},
  volume = {26},
  number = {1},
  pages = {37-40},
  url = {http://dx.doi.org/10.1029/1998GL900266},
  doi = {10.1029/1998GL900266}
}
Peria WJ, Kelley MC and Franz T (1999), "Double-probe measurements in field-aligned irregularities produced by intense electromagnetic radiation", Journal of Geophysical Research: Space Physics. Vol. 104(A4), pp. 6797-6804.
Abstract: We present the signature of filamentary field-aligned irregularities (FAI) in the artificially modified ionosphere using data from a rocket-borne floating double-probe gathered near the critical layer of the Arecibo HF heater beam. We model the double-probe signature as proportional to each filament's density gradient, in the plane perpendicular to the geomagnetic field. We find that this signature is consistent with the presence of a radially directed effective electric field Eeff within each of the over 180 filaments. The direction of Eeffis consistent with that of an ambipolar electric field associated with the rapid perpendicular diffusion of ions out of each filament, or with an apparent electric field due to an inward electron temperature gradient associated with the presence of hotter plasma inside each filament. Our model also gives an estimate of the impact parameter at which each filament is encountered. The mean square impact parameter shows the correct relation to the mean square filament transit time, assuming cylindrical field-aligned filaments. The consistency of these results confirms that the previously reported density depletions are quasi-steady, cylindrically symmetric, spatial structures. A small shift in the apparent angle between the double-probe boom and the filament-rocket velocity places a lower limit on the Earth-frame drift velocity of the filaments, away from the heater beam. Since the filaments are observed near the westward edge of the heater beam, well away from the bulk of the heater Poynting flux, we expect that the filaments are observed in the process of decaying, that is, that ions are diffusing inward rather than outward. Thus we identify Eeff as a temperature gradient and use it to estimate a minimum filament temperature enhancement of ~100 K.
BibTeX:
@article{Peria1999,
  author = {Peria, W. J. and Kelley, M. C. and Franz, T.},
  title = {Double-probe measurements in field-aligned irregularities produced by intense electromagnetic radiation},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {1999},
  volume = {104},
  number = {A4},
  pages = {6797-6804},
  url = {http://dx.doi.org/10.1029/1999JA900027},
  doi = {10.1029/1999JA900027}
}
Schubert G, Walterscheid RL, Hickey MP and Tepley CA (1999), "Observations and interpretation of gravity wave induced fluctuations in the O I (557.7 nm) airglow", Journal of Geophysical Research: Space Physics. Vol. 104(A7), pp. 14915-14924.
Abstract: Observations of fluctuations in the intensity and temperature of the O I (557.7 nm) airglow taken at Arecibo in 1989 are reported and interpreted on the assumption that they are caused by gravity waves propagating through the emission layer. The data give the magnitude of Krassovsky's ratio as 3.5 ± 2.2, at periods between about 5 and 10 hours. Comparison with theory shows that the gravity waves responsible for the measured airglow variations must have long wavelengths of several thousand kilometers. The observed phases of Krassovsky's ratio are in good agreement with theoretically predicted values at the long wavelengths and large periods for about half the cases. In the other cases, observed phases are near -180°, suggesting that the waves responsible for the airglow fluctuations have experienced strong reflections in the emission layer. The observations emphasize the importance of knowing the full altitude profiles of temperature and winds for extraction of wave information from the airglow fluctuations.
BibTeX:
@article{Schubert1999,
  author = {Schubert, G. and Walterscheid, R. L. and Hickey, M. P. and Tepley, C. A.},
  title = {Observations and interpretation of gravity wave induced fluctuations in the O I (557.7 nm) airglow},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {1999},
  volume = {104},
  number = {A7},
  pages = {14915-14924},
  url = {http://dx.doi.org/10.1029/1999JA900096},
  doi = {10.1029/1999JA900096}
}
Sethi NK, Mahajan KK and Pandey V (1999), "Bottomside Parameters B0, B1 from Arecibo Incoherent Scatter Radar Measurements", Advances in Space Research. Vol. 25(1), pp. 97-100.
Abstract: About 1500 electron density (Ne) profiles observed with the Arecibo incoherent scatter (I.S.) radar have been used to obtain the “best” B0 and B1 parameters by fitting the observed profiles to the IRI bottomside profile function. Seasonal and diurnal variations of these parameters are obtained. The relative difference between the “best fit” profiles and the observed I.S profiles is also studied. This difference is rather small during the night for all the seasons, but is very large during the day, especially during summer and equinox seasons, when an F1 layer is present. About 70 % of the profiles show rather good agreement.
BibTeX:
@article{Sethi1999,
  author = {Sethi, N K and Mahajan, K K and Pandey, V},
  title = {Bottomside Parameters B0, B1 from Arecibo Incoherent Scatter Radar Measurements},
  journal = {Advances in Space Research},
  year = {1999},
  volume = {25},
  number = {1},
  pages = {97-100},
  url = {http://dx.doi.org/10.1016/S0273-1177(99)00903-5},
  doi = {10.1016/S0273-1177(99)00903-5}
}
Sinha HSS, Raizada S and Misra RN (1999), "First simultaneous in situ measurement of electron density and electric field fluctuations during spread F in the Indian Zone", Geophysical Research Letters. Vol. 26(12), pp. 1669-1672.
Abstract: The paper presents results of in situ measurements of electron density and electric field fluctuations (ne, E'v and E'H) during a strong spread F event from the SHAR rocket range in India. Intermediate scale ne irregularities were observed in the F region valley over SHAR, which was earlier found to be free from irregularities. Experimental evidence of the validity of the image striation theory is provided through first simultaneous spectral measurement of electron density and electric field in the valley region. Correlation analysis of ne, E'v and E'H suggests the existence of a sheared flow of current below the F-peak. A new type of irregularity in the intermediate scale having a steep spectrum (n = -3.1) has also been detected in the valley region. A very sharp layer of ionization wherein the electron density increased by a factor of 50 in 10 km vertical extent was detected at 105 km.
BibTeX:
@article{Sinha1999,
  author = {Sinha, H. S. S. and Raizada, Shikha and Misra, R. N.},
  title = {First simultaneous in situ measurement of electron density and electric field fluctuations during spread F in the Indian Zone},
  journal = {Geophysical Research Letters},
  year = {1999},
  volume = {26},
  number = {12},
  pages = {1669-1672},
  url = {http://dx.doi.org/10.1029/1999GL900339},
  doi = {10.1029/1999GL900339}
}
Stening RJ (1999), "The lunar tide in sporadic E", Annales Geophysicae. Vol. 17(10), pp. 1344-1351.
Abstract: It seems that the wind shear theory is accepted for the explanation of sporadic E at mid and low latitudes. Some examples from Arecibo are displayed to show this. The effect of lunar tides should then modify the wind-shear theory in a manner that yields the observed features of the lunar tide in the critical frequency foEs and the height h'Es of the sporadic E. This is shown to imply that the phase of the lunar tide in h'Es should be the same as the phase of the lunar tide in the eastward wind and that the phase of the lunar tide in foEs is three hours later. Hourly values of foEs, f bEs (the blanketing critical frequency) and h'Es from several observatories are analysed for the lunar semidiurnal tide. It is found that the phase of the tide in foEs is often about 3 hours later than for h'Es in agreement with the theory. Seasonal variations in the tide are also examined with the statistically most significant results (largest amplitudes) usually occurring in summer. After reviewing the many difficulties associated with determining the lunar tide in Es, both experimentally and theoretically, the analysed phase results are compared with what might be expected from Hagan's global scale wave model. Agreement is only fair (a success rate of 69% among the cases examined) but probably as good as might be expected.
BibTeX:
@article{Stening1999,
  author = {Stening, R. J.},
  title = {The lunar tide in sporadic E},
  journal = {Annales Geophysicae},
  year = {1999},
  volume = {17},
  number = {10},
  pages = {1344-1351},
  url = {http://www.ann-geophys.net/17/1344/1999/angeo-17-1344-1999.html},
  doi = {10.1007/s00585-999-1344-2}
}
Aponte N (1998), "Radar studies of the equatorial F-region energy balance". Thesis at: CORNELL UNIVERSITY.
BibTeX:
@phdthesis{Aponte1998,
  author = {Aponte, N.},
  title = {Radar studies of the equatorial F-region energy balance},
  school = {CORNELL UNIVERSITY},
  year = {1998},
  url = {http://adsabs.harvard.edu/abs/1998PhDT........40A}
}
Cho JY, Sulzer MP and Kelley MC (1998), "Meteoric dust effects on D-region incoherent scatter radar spectra ", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 60(3), pp. 349-357.
Abstract: We extend the incoherent backscatter radar equation for the weakly ionized, collision-dominated case to include polydisperse charged dust, using the fluid-equation approach. Calculations with this equation show that the main effect of charged dust on the radar Doppler spectrum is to narrow it, except in the case of very small, negatively charged dust, which widens the spectrum. The results are encouraging for the use of incoherent scatter radar as an instrument for meteoric dust measurement. We also note that if the effects of meteoric dust are not taken into account, one may get a systematic bias in the D-region parameters deduced from the radar spectra. This may account for the discrepancy between observed and calculated spectra reported in earlier papers.
BibTeX:
@article{Cho1998,
  author = {John Y.N. Cho and Michael P. Sulzer and Michael C. Kelley},
  title = {Meteoric dust effects on D-region incoherent scatter radar spectra },
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {1998},
  volume = {60},
  number = {3},
  pages = {349-357},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682697001119},
  doi = {10.1016/S1364-6826(97)00111-9}
}
Earle G, Bishop R, Zhou Q and Wallace S (1998), "A comparative study of in-situ and remote intermediate layer measurements against wind model predictions of vertical ion drift ", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 60(13), pp. 1313 - 1330.
Abstract: Measurements from a sequence of rockets launched from Wallops Island (37.95°N, 75.47°W) on a single night in 1968 still provide the only in-situ data on the midlatitude intermediate layer phenomenon. TMA vapor trail observations made during this sequence of rocket flights were the first to experimentally examine the wind shear theory for the formation and slow downward motion of the layers. Using these rocket data from solar maximum, as well as several intermediate layer data sets from the Arecibo Observatory (18.35°N, 66.75°W) at solar minimum, we compare the location and motion of the layer observations to the predictions of two widely used thermospheric wind models: the HWM-93 thermospheric wind model and the TIEGCM. HWM-93 is an empirical model derived largely from measurements that had limited capabilities for determining night-time winds at lower thermospheric altitudes, and TIEGCM is a self consistent first principles model. Like an earlier study by Szuszczewicz et al., 1995, we find that some of our intermediate layer data agree quite well with the location of a convergent null in the meridional wind predicted by TIEGCM, but the correlation between layer altitude and the null in the vertical ion drift is in general poor. This finding contradicts theoretical expectations based on the two fluid plasma equations. We also demonstrate that uncertainties in the ion neutral collision frequency do not improve the agreement between the model vertical drifts and the observed layer behavior. Furthermore, we find some evidence that the HWM-93 model may overemphasize diurnal tidal effects in the winter, post-midnight period. The discrepancies found in this study demonstrate that our present understanding of midlatitude lower thermospheric wind systems is inadequate for predicting intermediate layer dynamics in the post-sunset period.
BibTeX:
@article{Earle19981313,
  author = {G.D. Earle and R.L. Bishop and Q.H. Zhou and S.P. Wallace},
  title = {A comparative study of in-situ and remote intermediate layer measurements against wind model predictions of vertical ion drift },
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {1998},
  volume = {60},
  number = {13},
  pages = {1313 - 1330},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682698000819},
  doi = {10.1016/S1364-6826(98)00081-9}
}
Fagundes P, Bittencourt J, Sahai Y, Takahashi H and Teixeira N (1998), "Plasma drifts inferred from thermospheric neutral parameters during geomagnetic storms at 23S", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 60(13), pp. 1303-1311.
Abstract: Nighttime thermospheric neutral winds and temperatures are derived from measurements of Doppler shifts and widths of the OI 630.0 nm airglow emission line, respectively, using a Fabry-Perot interferometer at Cachoeira Paulista (23°S, 45°W, 16°S dip latitude), Brazil. The observed nighttime East-West and North-South temperature gradients and neutral wind velocity variations are presented for two geomagnetic storm periods 7-10 July 1991 and 4-9 August 1991. Zonal plasma drifts inferred during an intense geomagnetic storm, from the nighttime neutral wind velocities and temporal temperature gradient variations, suggested that a strong zonal plasma drift (-240 m/s) on 9-10 July 1991 changed the direction of the zonal winds to westward at 01:30. Also it was noticed that, during the geomagnetic storm, the zonal temperature gradients were not well defined like those observed during quiet time. The meridional wind was towards the pole for the whole night during the geomagnetic storm of 9-10 July, a behaviour which is unusual during winter time (southern hemisphere) at Cachoeira Paulista. However, the meridional plasma drifts inferred did not show significant differences during the quiet and disturbed periods. The method presented to infer plasma drifts using the observed neutral parameters showed results comparable with those observed by incoherent scatter radar measurements at Arecibo.
BibTeX:
@article{Fagundes1998,
  author = {P.R. Fagundes and J.A. Bittencourt and Y. Sahai and H. Takahashi and N.R. Teixeira},
  title = {Plasma drifts inferred from thermospheric neutral parameters during geomagnetic storms at 23S},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {1998},
  volume = {60},
  number = {13},
  pages = {1303-1311},
  url = {http://dx.doi.org/10.1016/S1364-6826(98)00075-3},
  doi = {10.1016/S1364-6826(98)00075-3}
}
Gelinas LJ, Lynch KA, Kelley MC, Collins S, Baker S, Zhou Q and Friedman JS (1998), "First observation of meteoritic charged dust in the tropical mesosphere", Geophysical Research Letters. Vol. 25(21), pp. 4047-4050.
Abstract: We discuss a recent sounding rocket experiment which found charged dust in the Earth's tropical mesosphere. The dust detector was designed to measure small (5000–10000 amu) charged dust particles, most likely of meteoric origin. A 5 km thick layer of positively charged dust was found at an altitude of 90 km, in the vicinity of an observed sporadic sodium layer and sporadic E layer. The observed dust was positively charged in the bulk of the dust layer, but was negatively charged near the bottom.
BibTeX:
@article{Gelinas1998,
  author = {Gelinas, L. J. and Lynch, K. A. and Kelley, M. C. and Collins, S. and Baker, S. and Zhou, Q. and Friedman, J. S.},
  title = {First observation of meteoritic charged dust in the tropical mesosphere},
  journal = {Geophysical Research Letters},
  year = {1998},
  volume = {25},
  number = {21},
  pages = {4047-4050},
  url = {http://dx.doi.org/10.1029/1998GL900089},
  doi = {10.1029/1998GL900089}
}
Kelley M, Alcala C and Cho J (1998), "Detection of a meteor contrail and meteoric dust in the Earth's upper mesosphere", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 60(3), pp. 359 - 369.
Abstract: In 1983 a series of small rockets were launched from the Poker Flat Rocket Range near Fairbanks, Alaska to study what has come to be called Polar Mesospheric Summer Echoes (PMSE). We report here on a fortuitous simultaneous 50-MHz radar and rocket detection of what seems to be a meteor contrail produced over the Poker Flat Rocket Range. The two data sets are mutually consistent and taken together suggest some very interesting properties for the trails of large meteors. Most notable is the first evidence that the ablated material can coagulate into particles the order of 50 nm in radius. This estimate is based primarily on the fall speed deduced from both the Doppler shift of the VHG radar signal and the time rate of change of the target as it fell through the beam. In addition the very existence of the radar target, the extremely sharp edges of the trail, and the existence of electron density structures inside the trail more than an order of magnitude smaller than the Kolmogorov microscale, all require large charged aerosols and a very high Schmidt number. Curiously the environment leading to PMSE (the study of which was our primary mission), is very similar to the properties of a large meteor trail some minutes after it is formed. In the PMSE case ice particles grow and become charged by the plasma and, when more than half the charge is tied up on the ice, the plasma diffusion coefficient becomes so small that structure can be supported at VHF scattering scales. In the late-time meteor case large aerosols coagulate and tie up both natural charge in the plasma and the original meteor trail electrons. Following the work of Rosinski and Snow (1961) and Hunten et al. (1980) we conclude that the incident meteor was the order of 100 g and would have had a visual magnitude of about -5. This dust production process may resolve some open questions concerning long-lived meteor radar echoes. For example, in the event studied the electron density was well into the underdense condition and yet was detected for over 6 min. Classical meteor scatter theory has no explanation for such a long duration underdense event.
BibTeX:
@article{Kelley1998,
  author = {M.C. Kelley and C. Alcala and J.Y.N. Cho},
  title = {Detection of a meteor contrail and meteoric dust in the Earth's upper mesosphere},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {1998},
  volume = {60},
  number = {3},
  pages = {359 - 369},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682697001132},
  doi = {10.1016/S1364-6826(97)00113-2}
}
Kuo S, Huang J and Lee M (1998), "Parametric excitation of ion Bernstein waves by parallel-propagating langmuir waves in a collisional magnetoplasma", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 60(1), pp. 121-128.
Abstract: Langmuir waves propagating along the geomagnetic field are considered as pump waves for the parametric excitation of ion Bernstein waves and daughter Langmuir waves. Analysis of thresholds and growth rates for the conditions of Arecibo's heating experiments show that ten-meter scale ion Bernstein modes can be preferentially excited. This process competes with others that generate “stationary” (i.e., zero-frequency) density striations in the meter scale range. Limitations on the detection and diagnoses of ion Bernstein modes in the HF heating experiments are discussed.
BibTeX:
@article{Kuo1998121,
  author = {S.P. Kuo and J. Huang and M.C. Lee},
  title = {Parametric excitation of ion Bernstein waves by parallel-propagating langmuir waves in a collisional magnetoplasma},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {1998},
  volume = {60},
  number = {1},
  pages = {121-128},
  url = {http://dx.doi.org/10.1016/S1364-6826(97)00073-4},
  doi = {10.1016/S1364-6826(97)00073-4}
}
Lee MC, Riddolls RJ, Burke WJ, Sulzer MP, Kuo SP and Klien EMC (1998), "Generation of large sheet-like ionospheric plasma irregularities at Arecibo", Geophysical Research Letters. Vol. 25(16), pp. 3067-3070.
Abstract: Large-scale ionospheric plasma irregularities, generated by O-mode heater waves at Arecibo, are shown for the first time to have “sheet-like” structures. The irregularities are aligned with the magnetic meridional plane and have scale sizes ranging from a few hundred meters to a few kilometers. This interpretation is based on detailed considerations of sequential measurements of radar backscatter power, the controlling magnetic field geometry, and the deduced E × B plasma drift. The alignment of O-mode-generated irregularities with the magnetic meridional plane, and their disappearance during X-mode heating intervals are consistent with predictions of the thermal filamentation instability model.
BibTeX:
@article{Lee1998,
  author = {Lee, M. C. and Riddolls, R. J. and Burke, W. J. and Sulzer, M. P. and Kuo, S. P. and Klien, E. M. C.},
  title = {Generation of large sheet-like ionospheric plasma irregularities at Arecibo},
  journal = {Geophysical Research Letters},
  year = {1998},
  volume = {25},
  number = {16},
  pages = {3067-3070},
  url = {http://dx.doi.org/10.1029/98GL02322},
  doi = {10.1029/98GL02322}
}
Lee MC, Riddolls RJ, Burke WJ, Sulzer MP, Klien EMC, Rowlands MJ and Kuo SP (1998), "Ionospheric plasma bubble generated by Arecibo heater", Geophysical Research Letters. Vol. 25(5), pp. 579-582.
Abstract: During recent experiments ionospheric plasma bubbles were excited by the upgraded HF heater at Arecibo. These plasma bubbles were observed by radar in the midnight sector with the entire flux tube in darkness. A simple model is outlined to explain the dynamics of density depletions generated during O-mode wave heating of the F layer. We suggest that thermal expansion of plasma away from the heated volume leads to enhanced recombination along the flux tube. In the absence of photoionization sources, density depletions develop along the excited flux tube. The discontinuity of gravity-driven currents at the walls of the depleted region requires development of polarization electric fields. Eastward polarization electric fields of ~2.5 mV/m within the flux tube caused an observed plasma bubble to drift vertically at a speed of 70 m/s.
BibTeX:
@article{Lee1998a,
  author = {Lee, M. C. and Riddolls, R. J. and Burke, W. J. and Sulzer, M. P. and Klien, E. M. C. and Rowlands, M. J. and Kuo, S. P.},
  title = {Ionospheric plasma bubble generated by Arecibo heater},
  journal = {Geophysical Research Letters},
  year = {1998},
  volume = {25},
  number = {5},
  pages = {579-582},
  url = {http://dx.doi.org/10.1029/98GL00327},
  doi = {10.1029/98GL00327}
}
MacPherson B, Gonzales SA, Bailey GJ, Moffett RJ and Sulzer MP (1998), "The effects of meridional neutral winds on the O+-H+ transition altitude over Arecibo", Journal of Geophysical Research: Space Physics. Vol. 103(A12), pp. 29183-29198.
Abstract: Improvements to the way data are taken and analyzed at the Incoherent Scatter Radar Facility at Arecibo, Puerto Rico, mean that the transition altitude, where the O+ and H+ ion densities are equal, can now be studied at all local times throughout the solar cycle. These data show that the diurnal variation of the O+-H+ transition height is characterized by a rapid collapse following sunset, which is associated with the contraction of the plasma due to the rapidly decreasing plasma temperatures at this time. A corresponding increase in the transition altitude is seen at sunrise. The topside data also reveal that a secondary collapse, which is a nonthermal effect, is often observed at local times near midnight. Measurements taken during October 1994 and 1992 are presented and compared to results from the Sheffield University Plasmasphere Ionosphere Model (SUPIM) to study the effect of increasing solar EUV flux on the topside ionosphere. It is shown that SUPIM is able to model reasonably well the sunset and sunrise behavior of the transition altitude. In addition, the secondary collapse of the O+-H+ transition altitude is also studied. It is shown that this secondary collapse may be directly correlated to the well-known “midnight” collapse phenomenon of the F region over Arecibo. The magnitudes of the secondary collapse under low and moderate solar activity are compared, and it is shown that the secondary collapse is less pronounced during solar minimum conditions
BibTeX:
@article{MacPherson1998,
  author = {MacPherson, B and Gonzales, S A and Bailey, G J and Moffett, R J and Sulzer, M P},
  title = {The effects of meridional neutral winds on the O+-H+ transition altitude over Arecibo},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {1998},
  volume = {103},
  number = {A12},
  pages = {29183-29198},
  url = {http://dx.doi.org/10.1029/98JA02660},
  doi = {10.1029/98JA02660}
}
Melendez-Alvira DJ, Picone JM, Kelley OA, Zhou Q and Sulzer M (1998), "Histograms of Arecibo World Days Measurements and Linear-H Fits Between 1985 and 1995", NRL/MR/7640-98-8311. Vol. n/a-n/a, pp. n/a-n/a.
Abstract: This document presents histograms of linear-H model fits to electron density profiles measured with the incoherent scatter radar of the Arecibo Observatory in Puerto Rico during the World Days between 1985 and 1995. The linear-H model is a four-parameter analytical function, which is shown to fit the measured electron density profiles with better than 10% accuracy. The histograms show the distribution of the four model parameters as well as statistical measures of the model errors. In addition, the report presents histograms of electron temperature, ratios of electron and ion temperatures, and line-of-sight ion velocities at 589 km. The histograms characterize the ten years of Arecibo World Days, effectively showing a climatology of the actual ranges of both model and topside parameters.
BibTeX:
@article{Melendez-Alvira1998,
  author = {Melendez-Alvira, D J and Picone, J M and Kelley, O A and Zhou, Q and Sulzer, M},
  title = {Histograms of Arecibo World Days Measurements and Linear-H Fits Between 1985 and 1995},
  journal = {NRL/MR/7640-98-8311},
  year = {1998},
  volume = {n/a-n/a},
  pages = {n/a-n/a},
  url = {http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA358383}
}
Nossal S, Roesler FL and Coakley MM (1998), "Cascade excitation in the geocoronal hydrogen Balmer alpha line", Journal of Geophysical Research: Space Physics. Vol. 103(A1), pp. 381-390.
Abstract: This paper reports high-accuracy measurements of geocoronal Balmer &alpha; line profiles and demonstrates that the profiles are well fit with a model which includes cascade excitation by solar Lyman series radiation from n > 3 in addition to the direct excitation of n = 3 by solar Lyman &beta;. The increase in the signal-to-noise of our data is made possible by the use of the Fabry-Perot annular summing technique implemented at our Fabry-Perot facility at the University of Wisconsin's Pine Bluff Observatory. The new sensitivity has allowed us to make a detailed examination of line profile asymmetries and to conclude that they are compatible with predictions that of the order of 10% of the geocoronal Balmer &alpha; emission is caused by the cascade process. Cascade excitation alters the observed profile because it produces Balmer &alpha; emission along fine structure paths yielding slightly shifted wavelengths not present in direct Lyman &beta; excitation, which is the predominant excitation mechanism for geocoronal Balmer &alpha; . We discuss how fine structure excitation affects studies of non-Maxwellian exospheric hydrogen velocity distributions and effective temperatures through Balmer &alpha; line profile measurements. In a broader context, we consider how inclusion of the cascade excited emission in future radiation models can enhance their accuracy and their potential for assisting in the isolation in the data of shorter-term solar geophysical effects and longer timescale changes in exospheric hydrogen densities.
BibTeX:
@article{Nossal1998,
  author = {Nossal, S. and Roesler, F. L. and Coakley, M. M.},
  title = {Cascade excitation in the geocoronal hydrogen Balmer alpha line},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {1998},
  volume = {103},
  number = {A1},
  pages = {381-390},
  url = {http://dx.doi.org/10.1029/97JA02435},
  doi = {10.1029/97JA02435}
}
Noto J, Kerr RB, Shea EM, Waldrop LS, Fisher G, Rudy RJ, Hecht JH, Gonzalez SA, Sulzer MP and Garcia R (1998), "Evidence for recombination as a significant source of metastable helium", Journal of Geophysical Research: Space Physics. Vol. 103(A6), pp. 11595-11603.
Abstract: A Fabry-Perot spectrometer optimized for maximum near infrared (NIR) transmission and featuring a germanium detector with a quantum efficiency of 86% at 10,830 Å is used to measure the brightness and spectral width of the metastable helium emission in the upper thermosphere. Observations are made at the optical facility associated with the Millstone Hill Incoherent Scatter Radar site in Massachusetts and at the optical facility associated with the Arecibo Observatory in Arecibo, Puerto Rico. Using a spectral resolution of 0.117 Å, these are the first observations to isolate the metastable helium triplet 2p3P0,1,2–2s3S1 from nearby OH airglow contamination. Measured 10,830 Å brightness decays with shadow in a manner consistent with an emission that is due to resonant scattering of the solar 10,830 Å emission. Although the technique we describe was conceived as a powerful tool to measure upper thermospheric and exospheric temperatures, the data indicate a surprising increase of temperature with shadow height to values much greater than commonly ascribed to the near solar minimum thermosphere. We assert that the broad 10,830 Å spectral line widths, retrieved when the shadow heights are above ~300 km, are due to a nonthermal metastable helium population. This source of hot, metastable helium is very likely He+ recombination in the twilight. That conclusion is contrary to an historical understanding that the dominant source of metastable helium is the impact of photoelectrons with energies in excess of 19.8 eV with ground state helium.
BibTeX:
@article{Noto1998,
  author = {Noto, J. and Kerr, R. B. and Shea, E. M. and Waldrop, L. S. and Fisher, G. and Rudy, R. J. and Hecht, J. H. and Gonzalez, S. A. and Sulzer, M. P. and Garcia, R.},
  title = {Evidence for recombination as a significant source of metastable helium},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {1998},
  volume = {103},
  number = {A6},
  pages = {11595-11603},
  url = {http://dx.doi.org/10.1029/97JA03062},
  doi = {10.1029/97JA03062}
}
Osterman GB, Heelis RA and Bailey GJ (1998), "Effects of wind-induced ionization layers on ionospheric electrodynamics", Journal of Atmospheric and Solar-Terrestrial Physics. Vol. 60, pp. 107-113.
BibTeX:
@article{Osterman1998,
  author = {Osterman, G. B. and Heelis, R. A. and Bailey, G. J.},
  title = {Effects of wind-induced ionization layers on ionospheric electrodynamics},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
  year = {1998},
  volume = {60},
  pages = {107-113},
  doi = {10.1016/S1364-6826(97)00090-4}
}
Palmer RD, Larsen MF, Howell PB, Narayan RM and Kelley MC (1998), "Correction to “A new spatial interferometry capability using the Arecibo 430-MHz radar” by Robert D. Palmer et al.", Radio Science. Vol. 33(4), pp. 1035-1035.
BibTeX:
@article{Palmer1998,
  author = {Palmer, R D and Larsen, M F and Howell, P B and Narayan, R M and Kelley, M C},
  title = {Correction to “A new spatial interferometry capability using the Arecibo 430-MHz radar” by Robert D. Palmer et al.},
  journal = {Radio Science},
  year = {1998},
  volume = {33},
  number = {4},
  pages = {1035-1035},
  doi = {10.1029/98RS01630}
}
Qiu YH (1998), "A novel design for a giant Arecibo-type spherical radio telescope with an active main reflector", Monthly Notices of the Royal Astronomical Society. Vol. 301(3), pp. 827-830. Blackwell Science Ltd.
Abstract: A novel design for a giant spherical radio telescope is proposed. Instead of a fixed spherical reflecting surface such as with the 305-m Arecibo telescope, the illuminated portion of the reflecting surface is made to fit a paraboloid of revolution in real time by active control. A simple feed can thus be used, enabling the realization of broad bandwidth and full polarization. The actual design utilizes a karst depression which gives a spherical surface of 300-m radius, having an opening of 500-m diameter. The illuminated aperture is chosen to be 300 m, and the focal ratio is 0.46–0.48. With this geometry and the simple feeding system, a giant telescope with large sky coverage can be achieved at low cost. When the illuminated aperture is limited to 70–100 m, the area trackable can be extended to about 10° above the horizon.
BibTeX:
@article{Qiu1998,
  author = {Qiu, Yuhai H.},
  title = {A novel design for a giant Arecibo-type spherical radio telescope with an active main reflector},
  journal = {Monthly Notices of the Royal Astronomical Society},
  publisher = {Blackwell Science Ltd},
  year = {1998},
  volume = {301},
  number = {3},
  pages = {827-830},
  url = {http://dx.doi.org/10.1046/j.1365-8711.1998.02067.x},
  doi = {10.1046/j.1365-8711.1998.02067.x}
}
Showen RL and Slingeland A (1998), "Measuring lightning-induced ionospheric effects with incoherent scatter radar or with cross-modulation", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 60, pp. 951-956.
BibTeX:
@article{Showen1998,
  author = {Robert L. Showen and Alexander Slingeland},
  title = {Measuring lightning-induced ionospheric effects with incoherent scatter radar or with cross-modulation},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {1998},
  volume = {60},
  pages = {951-956},
  doi = {10.1016/S1364-6826(98)00016-9}
}
Turek RS, Roper RG and Brosnahan JW (1998), "Further direct comparisons of incoherent scatter and medium frequency radar winds from AIDA '89", Journal of Atmospheric and Terrestrial Physics. Vol. 60, pp. 337-347.
BibTeX:
@article{Turek1998,
  author = {Turek, R. S. and Roper, R. G. and Brosnahan, J. W.},
  title = {Further direct comparisons of incoherent scatter and medium frequency radar winds from AIDA '89},
  journal = {Journal of Atmospheric and Terrestrial Physics},
  year = {1998},
  volume = {60},
  pages = {337-347},
  doi = {10.1016/S1364-6826(97)00089-8}
}
Zhou Q (1998), "Two-day oscillation of electron concentration in thelower ionosphere ", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 60(17), pp. 1669 - 1677.
Abstract: A strong two-day modulation in electron concentration was observed by the Areciboincoherent scatter radar during January 21–28, 1993, in the altitude range between 85–94 km.The modulation of the electron density and the altitude variation of the lower edge of the electrondensity enhancement were associated with a quasi two-day planetary wave observed in the winds.On the days when the Lorentz force associated with the two-day wave pointed downward, theions were observed to penetrate to lower altitudes. At 90 km, the difference in electronconcentration between consecutive days was about 4000/cm3. Our analysis suggeststhat molecular ion transport can only account for less than 300/cm3 enhancement fortypical mesopause conditions. The large enhancement in electron concentration is likely due totransport of metallic ions from higher altitudes.
BibTeX:
@article{Zhou19981669,
  author = {Q.H. Zhou},
  title = {Two-day oscillation of electron concentration in thelower ionosphere },
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {1998},
  volume = {60},
  number = {17},
  pages = {1669 - 1677},
  url = {http://www.sciencedirect.com/science/article/pii/S136468269800100X},
  doi = {10.1016/S1364-6826(98)00100-X}
}
Zhou QH, Perillat P, Cho JYN and Mathews JD (1998), "Simultaneous meteor echo observations by large-aperture VHF and UHF radars", Radio Science. Vol. 33(6), pp. 1641-1654.
BibTeX:
@article{Zhou1998a,
  author = {Zhou, Q. H. and Perillat, P. and Cho, J. Y. N. and Mathews, J. D.},
  title = {Simultaneous meteor echo observations by large-aperture VHF and UHF radars},
  journal = {Radio Science},
  year = {1998},
  volume = {33},
  number = {6},
  pages = {1641-1654},
  doi = {10.1029/98RS02430}
}
Aponte N, Woodman RF, Swartz WE and Farley DT (1997), "Measuring ionospheric densities, temperatures, and drift velocities simultaneously at Jicamarca", Geophysical Research Letters. Vol. 24(22), pp. 2941-2944.
Abstract: Incoherent scatter autocorrelation function measurements are difficult to make in the F region at Jicamarca because of very strong clutter contamination by coherent echoes from unstable plasma waves in the E-region electrojet that are aligned with the magnetic field. We have developed a more effective way to deal with this clutter that improves the quality of the temperature (and composition when light ions are present) data. Other coherent echoes (much weaker than electrojet echoes but stronger than incoherent scatter) are also received through the antenna sidelobes from field-aligned irregularities in the 140–170 km altitude range during daytime. These latter echoes have a very narrow bandwidth, and so it is easy to measure their Doppler shift and obtain the vertical plasma drift velocity, which is proportional to the zonal electric field.
BibTeX:
@article{Aponte1997,
  author = {Aponte, Nestor and Woodman, Ronald F. and Swartz, Wesley E. and Farley, Donald T.},
  title = {Measuring ionospheric densities, temperatures, and drift velocities simultaneously at Jicamarca},
  journal = {Geophysical Research Letters},
  year = {1997},
  volume = {24},
  number = {22},
  pages = {2941-2944},
  url = {http://dx.doi.org/10.1029/97GL02898},
  doi = {10.1029/97GL02898}
}
Bailey G, Balan N and Su Y (1997), "The Sheffield University plasmasphere ionosphere model-a review", Journal of Atmospheric and Solar-Terrestrial Physics. Vol. 59(13), pp. 1541-1552.
Abstract: A brief description of the Sheffield University plasmasphere ionosphere model (SUPIM) is presented. In the model, time-dependent equations of continuity, momentum, and energy balance are solved along eccentric-dipole magnetic field lines for the densities, field-aligned fluxes and temperatures of the O+, H+, He+, N2+, O2+and NO+ ions, and the electrons. A review of some of the important results from recent studies of the model is presented. The studies show that during daytime, the equatorial plasma fountain can rise to altitudes of around 800 km at the magnetic equator and can cover magnetic latitudes of about ± 30 °. At regions outside the fountain, plasma flows towards the magnetic equator from both hemispheres and leads to the formation of an additional layer, the F3 layer, at latitudes close to the magnetic equator (± 10 °). The peak electron density of the F3 layer can exceed that of the F2 layer for a short period of time near noon when the ExB drift is large. Associated with the enhanced electron densities of the F3 layer are reduced electron temperatures. The modelled electron temperatures and densities are in accord with observations made by the Hinotori satellite at 600 km altitude. Closer agreement in the modelled and observed values is achieved if the phase and magnitude of the meridional wind, as given by the HWM90 thermospheric wind model, are modified in accordance with the observations made by the Japanese MU radar and the AE-E satellite. There is better agreement in the modelled and observed values when the equatorial vertical ExB drift velocity model used by SUPIM has an altitude variation in accord with the observations made by the AE-E satellite and at Arecibo.
BibTeX:
@article{Bailey1997,
  author = {G.J. Bailey and N. Balan and Y.Z. Su},
  title = {The Sheffield University plasmasphere ionosphere model-a review},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
  year = {1997},
  volume = {59},
  number = {13},
  pages = {1541-1552},
  url = {http://dx.doi.org/10.1016/S1364-6826(96)00155-1},
  doi = {10.1016/S1364-6826(96)00155-1}
}
Bauske R, Noel S and Prolss GW (1997), "Ionospheric storm effects in the nighttime E region caused by neutralized ring current particles", Annales Geophysicae. Vol. 15, pp. 300-305.
BibTeX:
@article{Bauske1997,
  author = {Bauske, R and Noel, S and Prolss, G W},
  title = {Ionospheric storm effects in the nighttime E region caused by neutralized ring current particles},
  journal = {Annales Geophysicae},
  year = {1997},
  volume = {15},
  pages = {300-305},
  doi = {10.1007/s00585-997-0300-2}
}
Cho JYN and Rottger J (1997), "An updated review of polar mesosphere summer echoes: Observation, theory, and their relationship to noctilucent clouds and subvisible aerosols", Journal of Geophysical Research: Atmospheres. Vol. 102(D2), pp. 2001-2020.
Abstract: Peculiar atmospheric radar echoes from the high-latitude summer mesosphere have spurred much research in recent years. The radar data (taken on frequency bands ranging from 2 to 1290 MHz) have been supplemented by measurements from an increasing arsenal of in situ (rocket borne) and remote sensing (satellites and lidars) instruments. Theories to explain these polar mesosphere summer echoes (PMSEs) have also proliferated. Although each theory is distinct and fundamentally different, they all share the feature of being dependent on the existence of electrically charged aerosols. It is therefore natural to assume that PMSEs are intimately linked to the other fascinating phenomenon of the cold summer mesopause, noctilucent clouds (NLCs), which are simply ice aerosols that are large enough to be seen by the naked eye. In this paper we critically examine both the data collected and the theories proposed, with a special focus on the relationship between PMSEs and NLCs.
BibTeX:
@article{Cho1997,
  author = {Cho, John Y. N. and Rottger, Jurgen},
  title = {An updated review of polar mesosphere summer echoes: Observation, theory, and their relationship to noctilucent clouds and subvisible aerosols},
  journal = {Journal of Geophysical Research: Atmospheres},
  year = {1997},
  volume = {102},
  number = {D2},
  pages = {2001-2020},
  url = {http://dx.doi.org/10.1029/96JD02030},
  doi = {10.1029/96JD02030}
}
Deng W, Salah JE, Clark RR, Franke SJ, Fritts DC, Hoffmann P, Kuerschner D, Manson AH, Meek CE, Murphy D, Nakamura T, Palo SE, Riggin DM, Roble RG, Schminder R, Singer W, Tsuda T, Vincent RA and Zhou Q (1997), "Coordinated global radar observations of tidal and planetary waves in the mesosphere and lower thermosphere during January 20–30, 1993", Journal of Geophysical Research: Space Physics. Vol. 102(A4), pp. 7307-7318.
Abstract: A multi-instrument global campaign involving incoherent scatter, medium frequency, and meteor wind radars was conducted during the period of January 20–30, 1993, to study the dynamics of the mesosphere and lower thermosphere. Data obtained from 15 radar stations covering a wide latitude range have been used to determine the global distribution of planetary and tidal waves during this 10-day campaign. Spectral analysis of the neutral winds measured by the radars in the altitude range from 80 to 130 km indicates the existence of a strong 48-hour wave near 90 km at latitudes between 40°N and 40°S that is present up to 108 km at 18°N. The semidiurnal tide is large at middle and high latitudes near 90 km and is predominant above 110 km, while the diurnal tide is observed to be particularly important in the upper mesosphere near 40° latitude. A least squares fit to the radar data is performed to obtain the amplitudes and phases of the tidal and 48-hour waves. Comparison with National Center for Atmospheric Research thermosphere-ionosphere-mesosphere general circulation model shows that the predictions from the model agree reasonably well with the observed global morphology of tidal wave amplitudes.
BibTeX:
@article{Deng1997,
  author = {Deng, W. and Salah, J. E. and Clark, R. R. and Franke, S. J. and Fritts, D. C. and Hoffmann, P. and Kuerschner, D. and Manson, A. H. and Meek, C. E. and Murphy, D. and Nakamura, T. and Palo, S. E. and Riggin, D. M. and Roble, R. G. and Schminder, R. and Singer, W. and Tsuda, T. and Vincent, R. A. and Zhou, Q.},
  title = {Coordinated global radar observations of tidal and planetary waves in the mesosphere and lower thermosphere during January 20–30, 1993},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {1997},
  volume = {102},
  number = {A4},
  pages = {7307-7318},
  url = {http://dx.doi.org/10.1029/96JA01630},
  doi = {10.1029/96JA01630}
}
Djuth FT, Sulzer MP, Elder JH and Wickwar VB (1997), "High-resolution studies of atmosphere-ionosphere coupling at Arecibo Observatory, Puerto Rico", Radio Science. Vol. 32(6), pp. 2321-2344.
Abstract: Very accurate measurements of electron density can be made at Arecibo Observatory, Puerto Rico, by applying the coded long-pulse (CLP) radar technique [Sulzer, 1986a] to plasma line echoes from daytime photoelectrons [Djuth et al., 1994]. In the lower thermosphere above Arecibo, background neutral waves couple to the ionospheric plasma, typically yielding ?1–3% electron density “imprints” of the waves. These imprints are present in all observations made to date; they are decisively detected at 30–60 standard deviations above the “noise level” imposed by the measurement technique. Complementary analysis and modeling efforts provide strong evidence that these fluctuations are caused by internal gravity waves. Properties of the neutral waves such as their period and vertical wavelength are closely mirrored by the electron density fluctuations. Frequency spectra of the fluctuations exhibit a high-frequency cutoff consistent with calculated values of the Brunt-Väisälä frequency. Vertical half wavelengths are typically in the range 2–25 km between 115- and 160-km altitude, and the corresponding phase velocities are always directed downward. Some waves have vertical wavelengths short enough to be quenched by kinematic viscosity. In general, the observed electron density imprints are relatively “clean” in that their vertical wavelength spectrum is characteristically narrow-banded. It is estimated that perturbations in the horizontal wind field as small as 2–4 m/s can give rise to the observed electron density fluctuations. However, the required wind speed can be significantly greater depending on the orientation of the neutral wave's horizontal wave vector relative to the geomagnetic field. Limited observations with extended altitude coverage indicate that wave imprints can be detected at thermospheric heights as high as 500 km.
BibTeX:
@article{Djuth1997,
  author = {Djuth, F. T. and Sulzer, M. P. and Elder, J. H. and Wickwar, V. B.},
  title = {High-resolution studies of atmosphere-ionosphere coupling at Arecibo Observatory, Puerto Rico},
  journal = {Radio Science},
  year = {1997},
  volume = {32},
  number = {6},
  pages = {2321-2344},
  url = {http://dx.doi.org/10.1029/97RS02797},
  doi = {10.1029/97RS02797}
}
Fesen CG, Emery BA, Buonsanto MJ, Zhou QH and Sulzer MP (1997), "Simulations of the F region during the January 1993 10-day campaign", Journal of Geophysical Research: Space Physics. Vol. 102(A4), pp. 7249-7265.
Abstract: The 10-day World Day campaign during January 20–30, 1993, provided an opportunity to test the current capability of the National Center for Atmospheric Research general circulation models and to conduct simple numerical experiments to investigate possible causes of day-to-day variability. Detailed data sets from the Arecibo and Millstone Hill incoherent scatter radars provided information on the middle- and low-latitude thermosphere and ionosphere during low solar activity which can be compared with model predictions. The theoretical model was used to examine the impact of varying two of the model inputs: the high-latitude energy and momentum sources and the semidiurnal tidal waves from the lower atmosphere. These exercises indicated that varying the high latitude inputs affect the simulations even to relatively low latitudes. The neutral winds in the models were responsive to the level of auroral activity and also to the magnitude of the waves from the lower atmosphere, particularly the neutral zonal winds. The simulated hmax were only affected at night by varying the model inputs. Use of the assimilative mapping of ionospheric electrodynamics (AMIE) technique is necessary to produce realistic quiet-time zonal ion drifts at low latitudes following local sunset. The ion and neutral temperatures proved nearly insensitive to the specifications of the auroral or the tidal inputs, particularly the temperatures at Arecibo. This is in contrast to the observations in which temperatures may vary by up to 100 K from day to day with more pronounced variability at night. In the models, only a large geomagnetic disturbance produced a perturbation in the temperatures but with magnitudes significantly smaller than those observed. The discrepancies may indicate an underestimate of the high-latitude Joule heating due to small-scale variability in magnetospheric electric fields, which would affect the neutral circulation and composition, and inadequate representation of the F region dynamo and conjugate effects in the models.
BibTeX:
@article{Fesen1997,
  author = {Fesen, C. G. and Emery, B. A. and Buonsanto, M. J. and Zhou, Q. H. and Sulzer, M. P.},
  title = {Simulations of the F region during the January 1993 10-day campaign},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {1997},
  volume = {102},
  number = {A4},
  pages = {7249-7265},
  url = {http://dx.doi.org/10.1029/96JA03312},
  doi = {10.1029/96JA03312}
}
Friedman JS, Tepley CA, Castleberg PA and Roe H (1997), "Middle-atmospheric Doppler lidar using an iodine-vapor edge filter", Optics Letters., Nov, 1997. Vol. 22(21), pp. 1648-1650. OSA.
Abstract: We present both modeled capabilities of and experimental data from a Doppler lidar for the stratosphere and the lower mesosphere that uses the edge of a molecular iodine filter in a differential measurement to provide frequency discrimination. Modeled results show a capability for wind measurements to an altitude of 55??km with 1.5-km resolution in 30??min.?Experimentally, wind-vector components from 18 to 45??km are measured every 20??min. The molecular-vapor filter provides great advantages with regard to system stability, operation in less-than-optimum weather conditions, and simplicity of data analysis.
BibTeX:
@article{Friedman:97,
  author = {J. S. Friedman and C. A. Tepley and P. A. Castleberg and H. Roe},
  title = {Middle-atmospheric Doppler lidar using an iodine-vapor edge filter},
  journal = {Optics Letters},
  publisher = {OSA},
  year = {1997},
  volume = {22},
  number = {21},
  pages = {1648--1650},
  url = {http://ol.osa.org/abstract.cfm?URI=ol-22-21-1648},
  doi = {10.1364/OL.22.001648}
}
Goldman M, Newman D, Drake R and Afeyan BB (1997), "Theory of convective saturation of Langmuir waves during ionospheric modification of a barium cloud", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 59(18), pp. 2335-2350.
Abstract: In recent experiments (Djuth, F. T., Sulzer, M. P., Elder, J. H. and Groves, K. M. (1995) Journal of Geophysical Research, 100, 17,347), a parametric decay instability was excited by an ordinarywave HF pump during an ionospheric chemical release from a rocket over Arecibo, PR, which created an artificial ‘barium ionosphere,’ with peak plasma frequency above the pump frequency, and a density gradient with a (short) 5 km scale length. Simultaneous incoherent scattering measurements revealed a strong initial asymmetry in the amplitudes of almost vertically upgoing versus downgoing measured plasma waves. We can account for this asymmetry in terms of linear convective saturation of parametrically unstable plasma waves propagating over a range of altitudes along geometric optics ray paths. Qualitative features of the frequency spectrum of the measured downgoing wave are in agreement with this model, although the theoretically predicted spectrum is narrower than observed. The observed altitude localization of the enhanced spectrum to a few range cells is consistent with the theory.
BibTeX:
@article{Goldman1997,
  author = {M.V. Goldman and D.L. Newman and R.Paul Drake and Bedros B. Afeyan},
  title = {Theory of convective saturation of Langmuir waves during ionospheric modification of a barium cloud},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {1997},
  volume = {59},
  number = {18},
  pages = {2335-2350},
  url = {http://dx.doi.org/10.1016/S1364-6826(96)00127-7},
  doi = {10.1016/S1364-6826(96)00127-7}
}
Gu YY, Gardner CS, Castleberg PA, Papen GC and Kelley MC (1997), "Validation of the Lidar In-Space Technology Experiment: stratospheric temperature and aerosol measurements", Applied Optics., Jul, 1997. Vol. 36(21), pp. 5148-5157. OSA.
Abstract: The Lidar In-Space Technology Experiment (LITE) was flown on STS-64 inSeptember 1994. The LITE employed a Nd:YAG laser operating at 1064, 532, and355 nm to study the Earth's lower atmosphere. In this paper weinvestigate the nighttime stratospheric aerosol and temperature measurementsderived from the 532- and 355-nm channels. The observations are compared withlidar observations obtained at Arecibo Observatory, Puerto Rico, and StarfireOptical Range, New Mexico, and with balloonsondes launched from the San Juanand Albuquerque airports. The backscatter ratios derived from the LITE andArecibo data between 15 and 30 km differ by less than 5 The Angstromcoefficients of the stratospheric aerosols derived from the 532- and 355-nmLITE channels exhibited only slight variation in altitude. The mean valuebetween 15 and 30 km derived from three different orbital segments atapproximately 20 textdegreeN and 35 textdegreeN was 1.7. The mean standard deviation wasapproximately 0.3. Temperature profiles were derived from the LITE data bycorrecting the 355-nm channel for aerosol scattering with the 532-nm signaland an assumed Angstrom coefficient. The rms differences between the correctedprofiles and the balloonsonde data were as low as 2 K in the 15--30-kmheight range. The results were not particularly sensitive to the choice of theAngstrom coefficient and suggest that accurate temperature profiles can bederived from the LITE data in the upper troposphere and lower stratosphereprovided that the aerosol loading is light.
BibTeX:
@article{Gu:97,
  author = {Yiyun Y. Gu and Chester S. Gardner and Paul A. Castleberg and George C. Papen and Michael C. Kelley},
  title = {Validation of the Lidar In-Space Technology Experiment: stratospheric temperature and aerosol measurements},
  journal = {Applied Optics},
  publisher = {OSA},
  year = {1997},
  volume = {36},
  number = {21},
  pages = {5148--5157},
  url = {http://ao.osa.org/abstract.cfm?URI=ao-36-21-5148},
  doi = {10.1364/AO.36.005148}
}
Hickey MP, Walterscheid RL, Taylor MJ, Ward W, Schubert G, Zhou Q, Garcia F, Kelly MC and Shepherd GG (1997), "Numerical simulations of gravity waves imaged over Arecibo during the 10-day January 1993 campaign", Journal of Geophysical Research. Vol. 102(A6), pp. 11475-11490.
Abstract: Recently, measurements were made of mesospheric gravity waves in the OI (5577 Å) nightglow observed from Arecibo, Puerto Rico, during January 1993 as part of a special 10-day campaign. Clear, monochromatic gravity waves were observed on several nights. By using a full-wave model that realistically includes the major physical processes in this region, we have simulated the propagation of two waves through the mesopause region and calculated the O(1S) nightglow response to the waves. Mean winds derived from both UARS wind imaging interferometer (WINDII) and Arecibo incoherent scatter radar observations were employed in the computations as were the climatological zonal winds defined by COSPAR International Reference Atmosphere 1990 (CIRA). For both sets of measured winds the observed waves encounter critical levels within the O(1S) emission layer, and wave amplitudes, derived from the requirement that the simulated and observed amplitudes of the O(1S) fluctuations be equal, are too large for the waves to be gravitationally stable below the emission layer. Some of the model coefficients were adjusted in order to improve the agreement with the measurements, including the eddy diffusion coefficients and the height of the atomic oxygen layer. The effect of changing the chemical kinetic parameters was investigated but was found to be unimportant. Eddy diffusion coefficients that are 10 to 100 times larger than presently accepted values are required to explain most of the observations in the cases that include the measured background winds, whereas the observations can be modeled using the nominal eddy diffusion coefficients and the CIRA climatological winds. Lowering the height of the atomic oxygen layer improved the simulations slightly for one of the simulated waves but caused a less favorable simulation for the other wave. For one of the waves propagating through the WINDII winds the simulated amplitude was too large below 82 km for the wave to be gravitationally stable, in spite of the adjustments made to the model parameters. This study demonstrates that an accurate description of the mean winds is an essential requirement for a complete interpretation of observed wave-driven airglow fluctuations.
BibTeX:
@article{Hickey1997,
  author = {Hickey, M P and Walterscheid, R L and Taylor, M J and Ward, W and Schubert, G. and Zhou, Q and Garcia, F and Kelly, M C and Shepherd, G G},
  title = {Numerical simulations of gravity waves imaged over Arecibo during the 10-day January 1993 campaign},
  journal = {Journal of Geophysical Research},
  year = {1997},
  volume = {102},
  number = {A6},
  pages = {11475-11490},
  url = {http://dx.doi.org/10.1029/97JA00181},
  doi = {10.1029/97JA00181}
}
Kelley MC and Miller CA (1997), "Electrodynamics of midlatitude spread F 3. Electrohydrodynamic waves? A new look at the role of electric fields in thermospheric wave dynamics", Journal of Geophysical Research: Space Physics. Vol. 102(A6), pp. 11539-11547.
Abstract: The study of atmospheric tides has long recognized the importance of electrodynamic or ohmic losses, in the form of JxB forces, on the strength of winds in the Earth's upper atmosphere. Now, recent observations of ionospheric and atmospheric phenomena (particularly, but not exclusively, at midlatitudes) are suggesting that electrodynamic processes may also be important for atmospheric buoyancy waves with periods as short as a few hours. During the daytime, passive ohmic losses may be responsible for a strong azimuthal filtering of buoyancy waves which limits their propagation in the upper atmosphere to near equatorward where there is a minimum of the JxB drag. At night, the active development of plasma instabilities, whose growth rate is also strongly azimuthally dependent, may not only minimize ion drag but may also feed energy into particular buoyancy waves to counteract the nighttime's enhanced molecular and thermal dissipation, thus creating a strong equatorward and westward orientation to observed traveling ionospheric disturbances. In all, the strength of the apparent coupling between buoyancy waves and ionospheric electrodynamics in the upper atmosphere may suggest the classification and study of a new form of electrohydrodynamic waves.
BibTeX:
@article{Kelley1997,
  author = {Kelley, Michael C. and Miller, Clark A.},
  title = {Electrodynamics of midlatitude spread F 3. Electrohydrodynamic waves? A new look at the role of electric fields in thermospheric wave dynamics},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {1997},
  volume = {102},
  number = {A6},
  pages = {11539-11547},
  url = {http://dx.doi.org/10.1029/96JA03841},
  doi = {10.1029/96JA03841}
}
Lee MC, Riddolls RJ, Vilece KD, Dalrymple NE, Rowlands MJ, Moriarty DT, Groves KM, Sulzer MP and Kuo SP (1997), "Laboratory reproduction of Arecibo experimental results: HF wave-enhanced Langmuir waves", Geophysical Research Letters. Vol. 24(2), pp. 115-118.
Abstract: Laboratory experiments at MIT using the Versatile Toroidal Facility (VTF) have produced “cascading” and “frequency-upshifted” spectra of HF wave-enhanced Langmuir waves resembling the spectra observed in Arecibo experiments. The VTF experiments are well-explained using the source mechanism proposed by Kuo and Lee [1992] to interpret observed Langmuir wave spectra at Arecibo, Puerto Rico. This mechanism is referred to as a nonlinear scattering of parametric decay instability (PDI)-excited Langmuir waves by “pre-existing” lower hybrid waves to preferentially produce anti-Stokes (i.e., frequency-upshifted) Langmuir waves. Recent radar spectral observations of anti-Stokes Langmuir waves at Arecibo with improved range and time resolution [Sulzer and Fejer, 1994] can be reasonably understood in terms of this mechanism.
BibTeX:
@article{Lee1997,
  author = {Lee, M. C. and Riddolls, R. J. and Vilece, K. D. and Dalrymple, N. E. and Rowlands, M. J. and Moriarty, D. T. and Groves, K. M. and Sulzer, M. P. and Kuo, S. P.},
  title = {Laboratory reproduction of Arecibo experimental results: HF wave-enhanced Langmuir waves},
  journal = {Geophysical Research Letters},
  year = {1997},
  volume = {24},
  number = {2},
  pages = {115-118},
  url = {http://dx.doi.org/10.1029/96GL03886},
  doi = {10.1029/96GL03886}
}
Mahajan KK, Sethi NK and Pandey V (1997), "The diurnal variation of E-F valley parameters from incoherent scatter measurements at Arecibo", Advances in Space Research. Vol. 20, pp. 1781-1784.
Abstract: The size and shape of the valley region between E and F layers is studied for nighttime conditions by using high resolution electron density profiles measured by the incoherent scatter radar at Arecibo, Puerto Rico, (18.3°N,66.7°W). Important valley parameters like width, depth and height of the valley minimum are derived from these measurements. By combining these nighttime results with our earlier daytime model (Mahajan, et.al, 1994), we now present a model for the full diurnal variation of the E–F valley parameters. Comparison with IRI-90 indicates significant differences between our model and the IRI valley model.
BibTeX:
@article{Mahajan1997,
  author = {Mahajan, K K and Sethi, N K and Pandey, V},
  title = {The diurnal variation of E-F valley parameters from incoherent scatter measurements at Arecibo},
  journal = {Advances in Space Research},
  year = {1997},
  volume = {20},
  pages = {1781-1784},
  url = {http://dx.doi.org/10.1016/S0273-1177(97)00591-7},
  doi = {10.1016/S0273-1177(97)00591-7}
}
Mathews J, Meisel D, Hunter K, Getman V and Zhou Q (1997), "Very High Resolution Studies of Micrometeors Using the Arecibo 430 MHz Radar", Icarus . Vol. 126(1), pp. 157 - 169.
Abstract: We present measured and inferred properties of a possible new class of “sporadic” micrometeors discovered during 18 January 1995 observations made using the very sensitive 430 MHz radar system located at Arecibo Observatory in Puerto Rico. Over 200 of these objects were observed in a 2-hr period near sunrise. The average speed was about 55 km/sec in a range of 45-63 km/sec. Approximately two-thirds of the observed trajectories were apparently nearly parallel with the vertical beam and occurred on the 93-102 km height interval. The observed occurrence rate of these meteor returns combined with the size the Arecibo beam points to a meteor flux corresponding-in the “classical” view-to 15th magnitude micrometeors. This information along with observed deceleration rates and radar scattering cross-sections of order 10-8m2, leads us to conclude that the majority of the meteors observed appear to be of order 1 ug in mass. The depth of atmospheric penetration and inferred perihelia, the majority of which lie mostly within the orbits of Mercury and Venus, point to compositions of dense refractory material. Retrograde orbits that lie well out of the plane of the ecliptic combined with the modeled effects of radiation pressure induced orbit decay suggest that these particles-with no obvious parent body-originated in the outer reaches of the solar system and that they may even be primordial in origin. It is suggested that most if not all of these particles are associated with the North Apex “source” of sporadic meteors reported by Jones and Brown (1993,Mon. Not. R. Astron. Soc.265, 524–532). Additionally, several possible radar scattering mechanisms are discussed, none of which seem completely satisfactory.
BibTeX:
@article{Mathews1997157,
  author = {J.D. Mathews and D.D. Meisel and K.P. Hunter and V.S. Getman and Q. Zhou},
  title = {Very High Resolution Studies of Micrometeors Using the Arecibo 430 MHz Radar},
  journal = {Icarus },
  year = {1997},
  volume = {126},
  number = {1},
  pages = {157 - 169},
  url = {http://www.sciencedirect.com/science/article/pii/S0019103596956419},
  doi = {10.1006/icar.1996.5641}
}
Mathews JD, Sulzer MP and Perillat P (1997), "Aspects of layer electrodynamics inferred from high-resolution ISR observations of the 80–270 km ionosphere", Geophysical Research Letters. Vol. 24(11), pp. 1411-1414.
Abstract: The Arecibo 430 MHz Incoherent Scatter Radar (ISR) has been used to observe vertical ionospheric electron concentration profiles in the 80–280 km altitude region at the highest sustained resolutions (150 m, 10 s) thus far reported for “ion-line” measurements. We present results that reveal layers and wave-like features in unprecedented detail and likely point to electrodynamic processes linking the E and F regions. Tidal Ion Layers (TILs) and sporadic E (Es) layers in the 100–110 km altitude region often display significant peaks and edges that appear in only one range gate (150 m). Also, previously unreported wave-like plasma structures—termed “ion rain”—with ~12 minutes apparent period, normalized amplitudes of 1–3%, and vertical wavelengths in excess of 30 km have been observed extending from base of the F-layer to the evening intermediate TIL with indications of coupling into the 90–110 km region below.
BibTeX:
@article{Mathews1997a,
  author = {Mathews, John D. and Sulzer, Michael P. and Perillat, Phil},
  title = {Aspects of layer electrodynamics inferred from high-resolution ISR observations of the 80–270 km ionosphere},
  journal = {Geophysical Research Letters},
  year = {1997},
  volume = {24},
  number = {11},
  pages = {1411-1414},
  url = {http://dx.doi.org/10.1029/97GL01320},
  doi = {10.1029/97GL01320}
}
Mendillo M, Baumgardner J, Nottingham D, Aarons J, Reinisch B, Scali J and Kelley M (1997), "Investigations of thermospheric-ionospheric dynamics with 6300-Å images from the Arecibo Observatory", Journal of Geophysical Research: Space Physics. Vol. 102(A4), pp. 7331-7343.
Abstract: Pilot observations were conducted at Arecibo, Puerto Rico, using an all-sky, image-intensified CCD camera system in conjunction with radar, ionosonde, and Global Positioning System (GPS) diagnostic systems during the periods January 19–28, 1993, and February 21 to August 22, 1995. These represent the first use of campaign mode operations of an imager at Arecibo for extended periods of F region observations. The January 1993 period (the so-called “10-day run”) yielded a rich data set of gravity wave signatures, perhaps the first case of direct imaging of thermospheric wave train properties in the F region. The 6-month 1995 campaign revealed two additional optical signatures of F region dynamics. A brightness wave in 6300 Å passing rapidly through the field of view (FOV) has been linked to meridional winds driven by the midnight temperature maximum (MTM) pressure bulge. On May 3, 1995, during a period of geomagnetic activity, a 6300-Å airglow depletion pattern entered the Arecibo FOV. Such effects represent the optical signatures of equatorial spread F instabilities that rise above the equator to heights near 2500 km, thereby affecting Arecibo's L = 1.4 flux tube.
BibTeX:
@article{Mendillo1997,
  author = {Mendillo, Michael and Baumgardner, Jeffrey and Nottingham, Daniel and Aarons, Jules and Reinisch, Bodo and Scali, James and Kelley, Michael},
  title = {Investigations of thermospheric-ionospheric dynamics with 6300-Å images from the Arecibo Observatory},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {1997},
  volume = {102},
  number = {A4},
  pages = {7331-7343},
  url = {http://dx.doi.org/10.1029/96JA02786},
  doi = {10.1029/96JA02786}
}
Miller CA and Kelley MC (1997), "Horizontal plasma flow at midlatitudes: More mechanisms and the interpretation of observations", Journal of Geophysical Research: Space Physics. Vol. 102(A6), pp. 11549-11555.
Abstract: The midlatitude ionosphere has been known for decades to exhibit correlated (or anticorrelated, depending on the coordinate system) perpendicular and parallel meridional ion velocities. This correlation is indicative of horizontal plasma flow, despite the highly magnetized character of the midlatitude F region. This coupling of the perpendicular and parallel dynamics is a consequence of extremely weak atmosphere-ionosphere coupling and the strong tendency for the neutral atmosphere to flow horizontally. Three physical mechanisms have previously been identified as effecting this coupling: ion drag, the F region dynamo, and enhanced gravity-driven diffusion. We point out some difficulties with one of these processes and present two additional mechanisms, wind-driven ionospheric equilibrium and gravity wave seeding of plasma instabilities, which can also result in horizontal plasma flow. Although these additional mechanisms further complicate the observational distinction between the possible mechanisms, we argue that an appropriately clustered array of instruments can still distinguish which mechanism is responsible for any particular geophysical occurrence.
BibTeX:
@article{Miller1997,
  author = {Miller, Clark A. and Kelley, Michael C.},
  title = {Horizontal plasma flow at midlatitudes: More mechanisms and the interpretation of observations},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {1997},
  volume = {102},
  number = {A6},
  pages = {11549-11555},
  url = {http://dx.doi.org/10.1029/96JA03842},
  doi = {10.1029/96JA03842}
}
Miller CA, Swartz WE, Kelley MC, Mendillo M, Nottingham D, Scali J and Reinisch B (1997), "Electrodynamics of midlatitude spread F: 1. Observations of unstable, gravity wave-induced ionospheric electric fields at tropical latitudes", Journal of Geophysical Research: Space Physics. Vol. 102(A6), pp. 11521-11532.
Abstract: In part 1 of our series exploring the role of electrical forces in midlatitude spread F, we present observations of an electrodynamically driven traveling ionospheric disturbance which passed over Arecibo Observatory between 22 and 24 AST on January 26, 1993. The total electric potential differences driving the wave were of the order of 1 kV. Our analysis indicates that this disturbance is the result of a midlatitude F region plasma instability seeded by a thermospheric gravity wave. Two novel measurements, in addition to typical incoherent scatter observations, were crucial to this determination: the use of 6300 Å airglow images from the coupling, energetics, and dynamics of atmospheric regions (CEDAR) allsky imager to track the two-dimensional, mesoseale dynamics of the disturbance and the use of a portable ionosonde to simultaneously measure the fieldline integrated ionospheric conductivity in the conjugate hemisphere. We have also determined that this disturbance, like several previously observed midlatitude disturbances, is consistent with our theoretical knowledge of the basic instability of the midlatitude ionosphere described originally by Perkins [1973].
BibTeX:
@article{Miller1997a,
  author = {Miller, C. A. and Swartz, W. E. and Kelley, M. C. and Mendillo, M. and Nottingham, D. and Scali, J. and Reinisch, B.},
  title = {Electrodynamics of midlatitude spread F: 1. Observations of unstable, gravity wave-induced ionospheric electric fields at tropical latitudes},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {1997},
  volume = {102},
  number = {A6},
  pages = {11521-11532},
  url = {http://dx.doi.org/10.1029/96JA03839},
  doi = {10.1029/96JA03839}
}
Miller CA (1997), "Electrodynamics of midlatitude spread F 2. A new theory of gravity wave electric fields", Journal of Geophysical Research: Space Physics. Vol. 102(A6), pp. 11533-11538.
Abstract: In this paper, we investigate the response of the nighttime, midlatitude ionosphere to atmospheric gravity waves in the presence of the global dynamo electric field. Previous theories of gravity wave-ionosphere interaction have neglected the zero-order electric field generated by the global dynamo. We find, however, that gravity wave winds carrying the ionosphere upward and downward along the tilted midlatitude magnetic field can cause spatial variations in the total conductive load experienced by the global circuit. In turn, these variations in ionospheric conductivity create divergences in the global current which produce local electric fields. Since ionospheric conductivity depends on altitude, any nighttime gravity wave which perturbs the height of the ionosphere may, through this mechanism, produce such fields. If true, the consequences of this interaction are potentially quite important. Gravity wave-induced electric fields may be the source of much of the day-to-day variation of the total ionospheric electric field; they may substantially alter the ionospheric electron density response to gravity waves; and they may seed ionospheric plasma instabilities. Further experimental investigations are necessary to test these predictions.
BibTeX:
@article{Miller1997b,
  author = {Miller, Clark A.},
  title = {Electrodynamics of midlatitude spread F 2. A new theory of gravity wave electric fields},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {1997},
  volume = {102},
  number = {A6},
  pages = {11533-11538},
  url = {http://dx.doi.org/10.1029/96JA03840},
  doi = {10.1029/96JA03840}
}
Nossal S, Roesler FL, Coakley MM and Reynolds RJ (1997), "Geocoronal hydrogen Balmer-alpha line profiles obtained using Fabry-Perot annular summing spectroscopy: Effective temperature results", Journal of Geophysical Research: Space Physics. Vol. 102(A7), pp. 14541-14553.
BibTeX:
@article{Nossal1997,
  author = {Nossal, S. and Roesler, F. L. and Coakley, M. M. and Reynolds, R. J.},
  title = {Geocoronal hydrogen Balmer-alpha line profiles obtained using Fabry-Perot annular summing spectroscopy: Effective temperature results},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {1997},
  volume = {102},
  number = {A7},
  pages = {14541-14553},
  doi = {10.1029/97JA00293}
}
Palmer RD, Larsen MF, Howell PB, Cho JYN, Narayanan RM and Kelley MC (1997), "A new spatial interferometry capability using the Arecibo 430-MHz radar", Radio Science. Vol. 32(2), pp. 749-755.
Abstract: This note describes the new spatial interferometry (SI) capability of the 430-MHz radar system of the Arecibo Observatory (AO). Three limitations exist when the 430-MHz radar is used for observations in the tropospheric and stratospheric regions. First, the AO radar currently has a lower height limitation of approximately 6 km because of the existing transmit/receive switch. Second, fading ground clutter limits the useful data which can be obtained and complicates the analysis. Third, the large mass of the feed system, which slows down beam steering, reduces the temporal resolution of any measurements requiring multiple beam positions. For these reasons, an SI system has been developed which will be shown to reduce these limitations. A brief description of the hardware is provided, and preliminary data are presented.
BibTeX:
@article{Palmer1997,
  author = {Palmer, Robert D. and Larsen, Miguel F. and Howell, Perry B. and Cho, John Y. N. and Narayanan, Ram M. and Kelley, Michael C.},
  title = {A new spatial interferometry capability using the Arecibo 430-MHz radar},
  journal = {Radio Science},
  year = {1997},
  volume = {32},
  number = {2},
  pages = {749-755},
  url = {http://dx.doi.org/10.1029/96RS03500},
  doi = {10.1029/96RS03500}
}
Palo SE, Hagan ME, Meek CE, Vincent RA, Burrage MD, McLandress C, Franke SJ, Ward WE, Clark RR, Hoffmann P, Johnson R, Kürschner D, Manson AH, Murphy D, Nakamura T, Portnyagin YI, Salah JE, Schminder R, Singer W, Tsuda T, Virdi TS and Zhou Q (1997), "An Intercomparison Between the CSWMn UARS and Ground Based Radar Observations: A Case study in January 1993", Annales Geophysicae. Vol. 15(9), pp. 1123-1141.
BibTeX:
@article{Palo1997,
  author = {Palo, S. E. and Hagan, M. E. and Meek, C. E. and Vincent, R. A. and Burrage, M. D. and McLandress, C. and Franke, S. J. and Ward, W. E. and Clark, R. R. and Hoffmann, P. and Johnson, R. and Kürschner, D. and Manson, A. H. and Murphy, D. and Nakamura, T. and Portnyagin, Y. I. and Salah, J. E. and Schminder, R. and Singer, W. and Tsuda, T. and Virdi, T. S. and Zhou, Q.},
  title = {An Intercomparison Between the CSWMn UARS and Ground Based Radar Observations: A Case study in January 1993},
  journal = {Annales Geophysicae},
  year = {1997},
  volume = {15},
  number = {9},
  pages = {1123-1141},
  doi = {10.1007/s00585-997-1123-x}
}
Pandey VK, Sethi NK and Mahajan K (1997), "Topside electron density distribution during sunrise and sunset conditions at Arecibo: comparison with IRI", Advances in Space Research. Vol. 20(9), pp. 1765-1768.
BibTeX:
@article{Pandey1997,
  author = {Pandey, V K and Sethi, N K and Mahajan, K},
  title = {Topside electron density distribution during sunrise and sunset conditions at Arecibo: comparison with IRI},
  journal = {Advances in Space Research},
  year = {1997},
  volume = {20},
  number = {9},
  pages = {1765-1768},
  doi = {10.1016/S0273-1177(97)00587-5}
}
Scali JL, Reinisch BW, Richards PG, Zhou Q, Sulzer M and Swartz WE (1997), "Comparison of incoherent scatter radar and Digisonde measurements with field line interhemispheric plasma modeled results at middle and low latitudes", Journal of Geophysical Research: Space Physics. Vol. 102(A4), pp. 7345-7355.
BibTeX:
@article{Scali1997,
  author = {Scali, J. L. and Reinisch, B. W. and Richards, P. G. and Zhou, Qihou and Sulzer, Mike and Swartz, W. E.},
  title = {Comparison of incoherent scatter radar and Digisonde measurements with field line interhemispheric plasma modeled results at middle and low latitudes},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {1997},
  volume = {102},
  number = {A4},
  pages = {7345-7355},
  doi = {10.1029/96JA03520}
}
Scali JL, Reinisch BW, Kelley MC, Miller CA, Swartz WE, Zhou QH and Radicella S (1997), "Incoherent scatter radar and Digisonde observations at tropical latitudes, including conjugate point studies", Journal of Geophysical Research: Space Physics. Vol. 102(A4), pp. 7357-7367.
BibTeX:
@article{Scali1997a,
  author = {Scali, J. L. and Reinisch, B. W. and Kelley, M. C. and Miller, C. A. and Swartz, W. E. and Zhou, Q. H. and Radicella, S.},
  title = {Incoherent scatter radar and Digisonde observations at tropical latitudes, including conjugate point studies},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {1997},
  volume = {102},
  number = {A4},
  pages = {7357-7367},
  doi = {10.1029/96JA03519}
}
Sridharan R, Chandra H, Das S, Sekar R, Sinha H, Raju D, Narayanan R, Raizada S, Misra R, Raghavarao R, Vyas G, Rao P, Ramarao P, Somayajulu V, Babu V and Danilov A (1997), "Ionization hole campaign—a coordinated rocket and ground-based study at the onset of equatorial spread-F: first results", Journal of Atmospheric and Solar-Terrestrial Physics. Vol. 59(16), pp. 2051 - 2067.
Abstract: A comprehensive multi-technique campaign involving the launch of two high altitude RH-560 rockets was carried out from Sriharikota (SHAR), India, a near-equatorial rocket launching station at the onset of equatorial spread-F, along with a host of ground-based complementary experiments at other locations spread over the country. The main objectives were to obtain the background ionospheric and thermospheric conditions at the onset of equatorial spread-F, and to be able to evaluate the relative importance of the various agencies, the neutral dynamics in particular. Multiple barium cloud releases, in situ plasma diagnostic measurements, along with complementary optical and radio probing experiments were carried out as a part of this campaign. The presence of large scale gradients in the ambient electric fields at ~185 km altitude and also of vertical winds of significant magnitudes at higher altitudes were found. The presence of large scale irregularities in the ion densities at heights above 250 km in a region of negative background density gradient is one of the significant new results. The details of the Ionization hole campaign along with the first results are presented and discussed in the context of the present knowledge of the phenomenon of equatorial spread-F.
BibTeX:
@article{Sridharan1997,
  author = {R. Sridharan and H. Chandra and S.R. Das and R. Sekar and H.S.S. Sinha and D.Pallam Raju and R. Narayanan and Shika Raizada and R.N. Misra and R. Raghavarao and G.D. Vyas and P.B. Rao and P.V.S. Ramarao and V.V. Somayajulu and V.V. Babu and A.D. Danilov},
  title = {Ionization hole campaign—a coordinated rocket and ground-based study at the onset of equatorial spread-F: first results},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
  year = {1997},
  volume = {59},
  number = {16},
  pages = {2051 - 2067},
  url = {http://www.sciencedirect.com/science/article/pii/S136468269700031X},
  doi = {10.1016/S1364-6826(97)00031-X}
}
Tepley CA (1997), "Current developments at Arecibo for research in the atmospheric sciences at low latitudes", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 59(13), pp. 1679-1686.
Abstract: We discuss several recent enhancements to the instrumentation that have taken place at the Arecibo Observatory. These improvements and equipment augmentations strengthen Arecibo's unique position as a facility capable of observing the total atmosphere and ionosphere in the tropics. The changes made, or those planned, affected both the radar and the optical systems. We begin with a description of the current status of the Gregorian Upgrade Project and describe the recent additions of supplementary instrumentation. We also note several examples of the latest experimental investigations of the atmosphere, conducted by visiting scientists and local staff, which range from very high altitudes to near the ground.
BibTeX:
@article{Tepley1997,
  author = {Craig A. Tepley},
  title = {Current developments at Arecibo for research in the atmospheric sciences at low latitudes},
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {1997},
  volume = {59},
  number = {13},
  pages = {1679-1686},
  doi = {10.1016/S1364-6826(96)00167-8}
}
Zhou QH and Sulzer MP (1997), "Incoherent scatter radar observations of the F-region ionosphere at Arecibo during January 1993 ", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 59(17), pp. 2213 - 2229.
Abstract: We report incoherent scatter radar observation of the F-region ion drift, plasma density, and electron and ion temperatures during the January 1993 World Day 10-day campaign. Although the observed ion drift during the geomagnetically quiet period agrees with previous observation in the horizontal direction to a large extent for similar geophysical conditions, the vertical ion drift shows a very large downward component throughout the entire day, which averages at about 20m s?1 near the F-region peak. Such a large average downward plasma drift has not been reported before at low latitudes. The downward motion of the F-region plasma comes mainly from the component along the geomagnetic field line, which is chiefly controlled by the meridional wind during the day and ambipolar diffusion during the night. The E × B drift also contributes to the downward motion of the F-region plasma during the nighttime although it is in anti-correlation with the variation introduced by the ion motion along the field line. During the geomagnetically disturbed period on 25 January, the ion drifts showed large departure from the quiet period. The perturbed eastward ion drift was highly correlated with that along the magnetic field, which may be indicative of the presence of field-aligned current. Our observation shows that the daytime electron concentration and electron temperature have contrasting correlations at different altitude ranges in the F-region. They are positively correlated below 180 km, anti-correlated between 220–400 km, not well correlated between 440–620 km, and again positively correlated at 660 km. While the positive correlation at 220–400 km has been observed previously and is well understood, the positive correlations below 180 km and at 660 km are less known and have not been systematically studied. Using the electron energy balance equation, we show that the contrasting relationships between electron concentration and electron temperature depend on the ion composition at lower altitudes; and on how electron heating via photoionization compares with thermal conduction at higher altitudes. Our observation shows that plasma motion, electron concentration and the thermal characteristics of the F-region ionosphere are all interrelated. We also present the day-to-day variability of plasma drift, electron and ion temperatures as well as electron concentration.
BibTeX:
@article{Zhou19972213,
  author = {Qihou H. Zhou and Michael P. Sulzer},
  title = {Incoherent scatter radar observations of the F-region ionosphere at Arecibo during January 1993 },
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {1997},
  volume = {59},
  number = {17},
  pages = {2213 - 2229},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682697000400},
  doi = {10.1016/S1364-6826(97)00040-0}
}
Zhou QH and Kelley MC (1997), "Meteor observations by the Arecibo 430 MHz incoherent scatter radar. II. Results from time-resolved observations ", Journal of Atmospheric and Solar-Terrestrial Physics . Vol. 59(7), pp. 739 - 752.
Abstract: We report high time resolution observations using the powerful Arecibo incoherent scatter radar (ISR). The majority of the meteor-like echoes observed lasted less than 50 ms at one range gate, although echoes lasting for a second were also occasionally observed. The latter may not necessarily be associated with meteors. Most of the meteor echoes in our observations have an effective radar cross-section of the order of 3 × 10?8m2, and an estimated electron line density (ELD) of the order of 4 × 109/m. The visual magnitude is approximately + 16, which is about two orders of magnitude fainter than the meteor echoes found in our time-integrated data (Zhou et al., 1995). The average echo power is positively correlated with the number of range bins in which an echo is detected. This characteristic, along with other experimental evidence, strongly suggests that the Arecibo 430 MHz radar is more sensitive to head-on meteors than to those arriving at an oblique angle. Although classical underdense scattering mechanisms may account for echoes having short range extensions, it is clear that they are insufficient to explain echoes having long range extensions. Some possible mechanisms are discussed. In particular, we suggest that Bragg scattering due to the irregular structure existing in a meteor trail is the most important scattering mechanism for the latter type of echoes in our observations. A plasma instability operating near the Arecibo wavelength is required.
BibTeX:
@article{Zhou1997739,
  author = {Qihou H. Zhou and Michael C. Kelley},
  title = {Meteor observations by the Arecibo 430 MHz incoherent scatter radar. II. Results from time-resolved observations },
  journal = {Journal of Atmospheric and Solar-Terrestrial Physics },
  year = {1997},
  volume = {59},
  number = {7},
  pages = {739 - 752},
  url = {http://www.sciencedirect.com/science/article/pii/S1364682696001034},
  doi = {10.1016/S1364-6826(96)00103-4}
}
MacPherson B (1997), "Models of thermal plasma behaviour in the terrestrial ionosphere : transport equations and Arecibo observations.". Thesis at: University of Sheffield.
BibTeX:
@phdthesis{,
  author = {Bryan MacPherson},
  title = {Models of thermal plasma behaviour in the terrestrial ionosphere : transport equations and Arecibo observations.},
  school = {University of Sheffield},
  year = {1997}
}
Fukao S, Takami T and Oliver WL (1996), "The Coupled Ionosphere and Thermosphere at Mid-Latitudes in the Asian Sector and Its Comparison with Other Locations", Journal of geomagnetism and geoelectricity. Vol. 48(1), pp. 113-124.
Abstract: The present paper reviews dynamical features of the mid-latitude ionosphere and thermosphere in the Asian sector as quantified by the MU radar at Shigaraki, Japan (35°N, 136°E) and compares these with dynamics reported for other locations. The thermospheric wind and temperature in the Asian sector differ from the wind and temperature measured at other mid-latitude locations. Furthermore, the perpendicular plasma drifts have strong resemblances to those predicted by current models, but their seasonal trends suggest a strong conjugate effect that has not been fully incorporated into our expectations of local behavior. These results provide additional evidence that global features cannot be described by a simple zonal mean. Finally, two features related to gravity waves are discussed. Gravity waves seem to be ubiquitous in the thermosphere and play an important role in creating a variety of electron density fluctuations and irregularities in the mid-latitude ionosphere. Tracking the progression of ionospheric gravity-wave effects between MU radar beams has allowed gravity wave packets to be identified and their dispersion relation to be determined. The character of ionospheric irregularities observed are consistent with their seeding by the Perkins mechanism.
BibTeX:
@article{1996113,
  author = {Shoichiro Fukao and Tomoyuki Takami and William L. Oliver},
  title = {The Coupled Ionosphere and Thermosphere at Mid-Latitudes in the Asian Sector and Its Comparison with Other Locations},
  journal = {Journal of geomagnetism and geoelectricity},
  year = {1996},
  volume = {48},
  number = {1},
  pages = {113-124},
  url = {https://www.jstage.jst.go.jp/article/jgg1949/48/1/48_1_113/_article},
  doi = {10.5636/jgg.48.113}
}
Cho JYN, Jurgens RF and Slade MA (1996), "High-resolution stratospheric dynamics measurements with the NASA/JPL Goldstone Solar System Radar", Geophysical Research Letters. Vol. 23(15), pp. 1909-1912.
Abstract: We have used, for the first time that we are aware of, the NASA/JPL Goldstone planetary radar to study the Earth's atmosphere. With its high bandwidth and power, we were able to achieve a height resolution of 20 m, which is significantly better than the usual 150-m resolution for stratospheric radars. Here we discuss the observation of a very thin scattering layer that persisted over several hours at the same height just above the tropopause. We question the assumption of turbulent radar scatter based on the available evidence, and also investigate the two-minute oscillation observed in the vertical velocity.
BibTeX:
@article{Cho1996,
  author = {Cho, John Y. N. and Jurgens, Raymond F. and Slade, Martin A.},
  title = {High-resolution stratospheric dynamics measurements with the NASA/JPL Goldstone Solar System Radar},
  journal = {Geophysical Research Letters},
  year = {1996},
  volume = {23},
  number = {15},
  pages = {1909-1912},
  url = {http://dx.doi.org/10.1029/96GL01570},
  doi = {10.1029/96GL01570}
}
Cho JY, Alcala CM, Kelley MC and Swartz WE (1996), "Further effects of charged aerosols on summer mesospheric radar scatter", Journal of Atmospheric and Terrestrial Physics . Vol. 58(6), pp. 661 - 672.
Abstract: In an earlier paper, we showed that charged aerosols play a crucial role in enhancing radar echoes from the summer polar mesosphere through reduced diffusion turbulent scatter and dressed aerosol scatter (Cho et al., 1992a). Here, we explore the effects of charged aerosols on radar scatter through ‘fossil’ turbulence and electron density depletion layers. We find that the former can produce radar scatter even after the decay of neutral gas turbulence, while the latter, which are probably produced by the scavenging of free electrons by ice particles, are a candidate for causing partial reflection or Fresnel scatter. Furthermore, we examine the mutual aerosol interaction restriction on dressed aerosol scatter more closely. We find that a high ambient electron density and low aerosol number density are needed for effective dressed aerosol scatter to occur. We then show that very small (less than 1 nm radii), negatively charged aerosols enhance electron diffusivity, and thus inhibit radar scatter. Also, ice aerosol sedimentation, in the light of the reduced diffusion theory, leads us to conclude that the statistical peak in Polar Mesospheric Summer Echoes (PMSE) power should be located between the mean mesopause and the average noctilucent cloud (NLC) height, which agrees with observations. Finally, we invoke time lags in the ice particle formation cycle to account for the observed non-correlation between PMSE and NLC occurrence.
BibTeX:
@article{Cho1996a,
  author = {John Y.N. Cho and Christian M. Alcala and Michael C. Kelley and Wesley E. Swartz},
  title = {Further effects of charged aerosols on summer mesospheric radar scatter},
  journal = {Journal of Atmospheric and Terrestrial Physics },
  year = {1996},
  volume = {58},
  number = {6},
  pages = {661 - 672},
  url = {http://www.sciencedirect.com/science/article/pii/0021916995000658},
  doi = {10.1016/0021-9169(95)00065-8}
}
Coakley MM, Roesler FL, Reynolds RJ and Nossal S (1996), "Fabry--Perot CCD annular-summing spectroscopy: study and implementation for aeronomy applications", Applied Optics., Nov, 1996. Vol. 35(33), pp. 6479-6493. OSA.
Abstract: The technique of Fabry--Perot CCD annular-summing spectroscopy, with particular emphasis on applications in aeronomy, is discussed. Parameter choices for optimizing performance by the use of a standard format CCD array are detailed. Spectral calibration methods, techniques for determining the ring pattern center, and effects imposed by limited radial resolution caused by superpixel size, variable by on-chip binning, are demonstrated. The technique is carefully evaluated experimentally relative to the conventional scanning Fabry--Perot that uses a photomultiplier detector. We evaluate three extreme examples typical of aeronomical spectroscopy using calculated signal-to-noise ratios. Predicted sensitivity gains of 10--30 are typical. Of the cases considered, the largest savings in integration time are estimated for the day sky thermospheric O1D case, in which the bright sky background dominates the CCD read noise. For profile measurements of faint night sky emission lines, such as exospheric hydrogen Balmer-$, long integration times are required to achieve useful signal-to-noise ratios. In such cases, CCD read noise is largely overcome. Predictions of a factor of 10--15 savings in integration time for night sky Balmer-$ observations are supported by field tests. Bright, isolated night sky lines such as thermospheric O1D require shorter integration times, and more modest gains dependent on signal level are predicted. For such cases it appears from estimate results that the Fabry--Perot CCD annular-summing technique with a conventional rectangular format may be outperformed by a factor of 2--5 by special CCD formats or by unusual optical coupling configurations that reduce the importance of read noise, based on the ideal transmission for any additional optics used in these configurations.
BibTeX:
@article{Coakley:96,
  author = {M. M. Coakley and F. L. Roesler and R. J. Reynolds and S. Nossal},
  title = {Fabry--Perot CCD annular-summing spectroscopy: study and implementation for aeronomy applications},
  journal = {Applied Optics},
  publisher = {OSA},
  year = {1996},
  volume = {35},
  number = {33},
  pages = {6479--6493},
  url = {http://ao.osa.org/abstract.cfm?URI=ao-35-33-6479},
  doi = {10.1364/AO.35.006479}
}
Coakley M. M.; Roesler FLRRJNS (1996), "Fabry-Perot CCD annular-summing spectroscopy: study and implementation for aeronomy applications", Applied Optics. Vol. 35, pp. 6479-6493. Optical Society of America.
Abstract: The technique of Fabry-Perot CCD annular-summing spectroscopy, with particular emphasis on applications in aeronomy, is discussed. Parameter choices for optimizing performance by the use of a standard format CCD array are detailed. Spectral calibration methods, techniques for determining the ring pattern center, and effects imposed by limited radial resolution caused by superpixel size, variable by on-chip binning, are demonstrated. The technique is carefully evaluated experimentally relative to the conventional scanning Fabry-Perot that uses a photomultiplier detector. We evaluate three extreme examples typical of aeronomical spectroscopy using calculated signal-to-noise ratios. Predicted sensitivity gains of 10–30 are typical. Of the cases considered, the largest savings in integration time are estimated for the day sky thermospheric O1D case, in which the bright sky background dominates the CCD read noise. For profile measurements of faint night sky emission lines, such as exospheric hydrogen Balmer-&alpha; , long integration times are required to achieve useful signal-to-noise ratios. In such cases, CCD read noise is largely overcome. Predictions of a factor of 10-15 savings in integration time for night sky Balmer-&alpha; observations are supported by field tests. Bright, isolated night sky lines such as thermospheric O1D require shorter integration times, and more modest gains dependent on signal level are predicted. For such cases it appears from estimate results that the Fabry–Perot CCD annular-summing technique with a conventional rectangular format may be outperformed by a factor of 2-5 by special CCD formats or by unusual optical coupling configurations that reduce the importance of read noise, based on the ideal transmission for any additional optics used in these configurations.
BibTeX:
@article{Coakley1996,
  author = {Coakley, M. M.; Roesler, F. L.; Reynolds, R. J.; Nossal, S.},
  title = {Fabry-Perot CCD annular-summing spectroscopy: study and implementation for aeronomy applications},
  journal = {Applied Optics},
  publisher = {Optical Society of America},
  year = {1996},
  volume = {35},
  pages = {6479-6493},
  url = {http://dx.doi.org/10.1364/AO.35.006479},
  doi = {10.1364/AO.35.006479}
}
Flaherty JP, Kelley MC, Seyler CE and Fitzgerald TJ (1996), "Simultaneous VHF and transequatorial HF observations in the presence of bottomside equatorial spread F", Journal of Geophysical Research: Space Physics. Vol. 101(A12), pp. 26811-26818.
Abstract: Simultaneous transequatorial HF and VHF incoherent scatter measurements were conducted in Peru in January 1994. On the evening of January 13, conditions as measured at VHF by the Jicamarca Radio Observatory were comparatively mild. The spread F observed on this evening was confined to the bottomside of the F layer and relatively weak. Yet dramatic propagation effects were seen in the HF. Strong off great circle signals with more than 10 Hz in Doppler spread were measured. Large spreads in angle of arrival, as much as 20 deg, were also seen. The strength of the off great circle returns are comparable to the strength of signals arriving from the direction of the great circle and are believed to result from total reflections from horizontal gradients in the ionosphere. Jicamarca VHF measurements substantiate this hypothesis. We present data from a single evening during which two separate events occurred. From the combined VHF and HF measurements, we conclude that the source of the off great circle reflections consists of a longitudinal density gradient which is immediately followed by a region of unstable plasma. The unstable plasma affecting the HF signals is shown to consist of a sequence of finger-like structures having a nominal separation of 15 km which remain below the height of maximum F region electron density.
BibTeX:
@article{Flaherty1996,
  author = {Flaherty, J. P. and Kelley, M. C. and Seyler, C. E. and Fitzgerald, T. J.},
  title = {Simultaneous VHF and transequatorial HF observations in the presence of bottomside equatorial spread F},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {1996},
  volume = {101},
  number = {A12},
  pages = {26811-26818},
  url = {http://dx.doi.org/10.1029/96JA01115},
  doi = {10.1029/96JA01115}
}
Gonzalez SA and Sulzer MP (1996), "Detection of He+ layering in the topside ionosphere over Arecibo during equinox solar minimum conditions", Geophysical Research Letters. Vol. 23(18), pp. 2509-2512.
Abstract: We describe recent developments in and results from topside incoherent scatter radar (ISR) measurements at Arecibo, PR, emphasizing helium ion measurements. Recent improvements in the data taking modes and the data processing permit isolation of the concentrations of oxygen, helium and hydrogen ions between the F region peak and 2000 km with about 10 minute time resolution. The need for the three ion non-linear least squares fits is justified by use of the goodness of fit; a two ion fit is shown to be unacceptable. The new measurements are optimized for the rapid height variations in the solar minimum nighttime ionosphere by replacing the traditional 1 ms pulse with a 500 µs pulse. We show results from one day of a five day experiment during the Spring of 1994. For these equinox solar minimum conditions, the altitude distribution of the helium ions usually has a maximum near the O+ to H+ transition altitude (ht), forming a distinct layer, most noticeable during the night. The maximum helium ion concentrations tend to be quite low, 2 or 3 × 10³ cm-3, or 10-20% of the topside plasma at the peak of the He+ layer. The transition altitude, ht, varies from about 1200 km to 1400 km during the day to near 500 km at night, and the He+ layer follows this altitude variation. Finally we show that the location of the layer near ht and its intensification during the night can be explained using ambipolar diffusion equations.
BibTeX:
@article{Gonzalez1996,
  author = {Gonzalez,, Sixto A. and Sulzer, Michael P.},
  title = {Detection of He+ layering in the topside ionosphere over Arecibo during equinox solar minimum conditions},
  journal = {Geophysical Research Letters},
  year = {1996},
  volume = {23},
  number = {18},
  pages = {2509-2512},
  url = {http://dx.doi.org/10.1029/96GL02212},
  doi = {10.1029/96GL02212}
}
Gulyaeva T, Mahajan K and Sethi N (1996), "Modification of IRI half-density height option for low latitudes", Advances in Space Research. Vol. 18(6), pp. 149-152.
Abstract: The International Reference Ionosphere provides an option for using the half-density height h0.5 when determining the bottom-side electron density profile. For low latitudes the ratio h0.5/hmF2 (peak height) is modified using Arecibo incoherent scatter electron density profiles. A linear variation with latitude of the coefficients is introduced for nighttime and daytime in case h0.5 is located above the F1 layer heights (class ‘A’). The profile semithickness is large when 0.5NmF2 value is less than NmF1 (class ‘B’). At low latitudes class ‘B’ occurs during the first half of the day; at mid-latitudes, however, the Digisonde data from Millstone Hill show these to occur during most of the daytime.
BibTeX:
@article{Gulyaeva1996,
  author = {T.L. Gulyaeva and K.K. Mahajan and N.K. Sethi},
  title = {Modification of IRI half-density height option for low latitudes},
  journal = {Advances in Space Research},
  year = {1996},
  volume = {18},
  number = {6},
  pages = {149-152},
  url = {http://dx.doi.org/10.1016/0273-1177(95)00916-7},
  doi = {10.1016/0273-1177(95)00916-7}
}
Habbal SR, Mossman A, Gonzalez R and Esser R (1996), "Radio, visible, and X ray emission preceding and following a coronal mass ejection", Journal of Geophysical Research: Space Physics. Vol. 101(A9), pp. 19943-19955.
Abstract: This study uses both disk and limb observations to examine the changing conditions of the low solar corona, below 1.5 Rs, preceding and following a coronal mass ejection observed on the west limb on April 12, 1993. The disk observations comprise 90 cm (333 MHz) radio and daily Yohkoh soft X ray measurements, while the limb observations include measurements of emission from X rays, Fe X 637.4 nm and Fe XIV 530.3 nm coronal lines, and broadband Thomson-scattered white light. The analysis of the disk and limb observations shows that throughout the 3 days of consecutive observations, the occurrence and persistence of nonthermal emission at 90 cm, also known as type I noise storm emission, were associated with large-scale magnetic structures where the coronal mass ejection eventually occurred. Other than a subsequent flare observed in X rays at the limb, the changes in the coronal emission preceding and following the event were not markedly different from changes in other neighboring structures. The analysis of this novel combination of data supports the current view that coronal mass ejections are a cause rather than a consequence of the “classical” solar activity in the low corona. The radio observations, on the other hand, suggest that a connection between a noise storm and a coronal mass ejection exists. However, they do not necessarily imply that the noise storm actually initiates the event.
BibTeX:
@article{Habbal1996,
  author = {Habbal, Shadia R. and Mossman, Amy and Gonzalez, Raymond and Esser, Ruth},
  title = {Radio, visible, and X ray emission preceding and following a coronal mass ejection},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {1996},
  volume = {101},
  number = {A9},
  pages = {19943-19955},
  url = {http://dx.doi.org/10.1029/96JA01190},
  doi = {10.1029/96JA01190}
}
Hagen JB and Baumgartner HA (1996), "Backscatter gain of aperture antennas", Radio Science. Vol. 31(4), pp. 693-699.
Abstract: It is well known that the conventional on-axis gain of an aperture-type antenna is maximized when the aperture illumination pattern has uniform amplitude and phase. For backscatter radar measurements, however, the distributed target brings the off-axis gain into play, and the sensitivity is proportional to the square of the gain averaged over the solid angle of the beam. It has been assumed that this backscatter gain, like on-axis gain, is maximized when the illumination is uniform. We show that this is not quite the case; for a fixed aperture area the backscatter gain can be increased at least 6% by using the kind of amplitude taper that reduces sidelobe levels. It is also well known that the maximum on-axis gain is proportional to the area of the aperture but independent of the shape. We show that this is not the case for backscatter gain.
BibTeX:
@article{Hagen1996,
  author = {Hagen, Jon B. and Baumgartner, Hans A.},
  title = {Backscatter gain of aperture antennas},
  journal = {Radio Science},
  year = {1996},
  volume = {31},
  number = {4},
  pages = {693-699},
  url = {http://dx.doi.org/10.1029/96RS01095},
  doi = {10.1029/96RS01095}
}
Howell PB, Palmer R, Narayanan R, Larsen MF and Cho JYN (1996), "Preliminary results from the Arecibo 430 MHz spatial interferometry system", Geoscience and Remote Sensing Symposium, 1996. IGARSS '96. 'Remote Sensing for a Sustainable Future.'., In Geoscience and Remote Sensing Symposium, 1996. IGARSS '96. 'Remote Sensing for a Sustainable Future.', International. Vol. 4, pp. 1926-1928.
Abstract: The 430 MHz radar system of the Arecibo Observatory (AO) possesses one of the largest power-aperture products in the world. The aperture is effectively 200-300 m and the peak power is approximately 2.5 MW. Designed originally for ionospheric and radioastronomy, the AO is built into a natural bowl in the Puerto Rican terrain. The feed system is directed downward, toward the dish, and then reflected into the atmosphere. As a result, the platform which houses the feed systems must be very stable. The structure is suspended by a network of steel cables strung from large concrete towers. In total, the feed platform weighs approximately 600 tons and cannot be moved rapidly. This results in an enormous amount of wasted time during the steering of the beam, which can take up to 30 min. Doppler beam swinging (DBS) techniques have been attempted with the system but adequate temporal resolution is difficult to obtain. The DBS technique determines the wind velocity by obtaining the Doppler shift of the scattered signal from several beam directions, which are converted into radial velocity estimates. Subsequently, the radial velocity estimate can be used to derive the overall wind field. DBS techniques have been attempted with the AO system but adequate temporal resolution is difficult to obtain because of the slow beam steering. Multi-receiver techniques, which use only a single beam direction, can alleviate the temporal resolution concern since no beam steering is needed. In a collaborative effort a spatial interferometric (SI) system, i.e., multireceiver, has been built and will be installed at the AO. Preliminary tests have been performed in 1995 with final installation planned for the spring of 1996. The results of the tests are discussed
BibTeX:
@article{Howell1996,
  author = {Howell, P. B. and Palmer, R.D. and Narayanan, R.M. and Larsen, M. F. and Cho, J. Y N},
  title = {Preliminary results from the Arecibo 430 MHz spatial interferometry system},
  booktitle = {Geoscience and Remote Sensing Symposium, 1996. IGARSS '96. 'Remote Sensing for a Sustainable Future.', International},
  journal = {Geoscience and Remote Sensing Symposium, 1996. IGARSS '96. 'Remote Sensing for a Sustainable Future.'},
  year = {1996},
  volume = {4},
  pages = {1926-1928},
  url = {http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=516844&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D516844},
  doi = {10.1109/IGARSS.1996.516844}
}
Huang X and Reinisch B (1996), "Vertical electron density profiles from the Digisonde network ", Advances in Space Research . Vol. 18(6), pp. 121-129.
Abstract: The global Digisonde network provides a vast volume of ionogram-derived electron density profile data from some 50 stations. The current true height inversion program NHPC differs significantly from the original algorithms developed for real time calculation on PC 286 machines. NHPC successfully inverts about 90% of the autoscaled ionograms. A stand-alone version of NHPC can invert h'(f) traces from any digital or analog ionogram. For each layer, the N(h) profile is expressed in terms of shifted Chebyshev polynomials with a logarithmic argument containing the starting plasma frequency and the critical frequency of the layer. The peak height and a set of coefficients specify the electron density distribution of each layer. A valley model derived from incoherent scatter observations at Arecibo describes the E-F trasition. The frequent problem of missing h'(f) data points at the beginning of a trace is addressed by analytical expansion in the true height (profile) domain rather than by direct extrapolation of the h'(f) trace. The validity of the Digisonde NHPC profiles has been verified by comparison with incoherent scatter radar profiles.
BibTeX:
@article{Huang1996,
  author = {Xueqin Huang and B.W. Reinisch},
  title = {Vertical electron density profiles from the Digisonde network },
  journal = {Advances in Space Research },
  year = {1996},
  volume = {18},
  number = {6},
  pages = {121-129},
  url = {http://dx.doi.org/10.1016/0273-1177(95)00912-4},
  doi = {10.1016/0273-1177(95)00912-4}
}
Huang C-S and Kelley MC (1996), "Numerical simulations of gravity wave modulation of midlatitude sporadic E layers", Journal of Geophysical Research: Space Physics. Vol. 101(A11), pp. 24533-24543.
Abstract: We have used a computer simulation to study gravity wave modulation of midlatitude sporadic E (Es) layers. It is shown that a horizontally stratified Es layer may be deformed by gravity waves and become a large-scale wavelike structure. Spatial resonance is not required for significant modulations to form. For a southward propagating gravity wave the south side sections of the wavelike deformed Es layer may overturn and appear as field-aligned features stretching about 10 km in altitude. The deformed Es layer drifts at a velocity larger than neutral wind velocity but smaller than the phase velocity of the gravity wave. The scale length of the wavelike Es layers is determined by the horizontal wavelength of the gravity wave. If there are two or more Es layers modulated simultaneously by a gravity wave, the height dependence of the amplitude of the wave must be taken into account. The Es layer at lower altitude is weakly disturbed if the gravity wave has only a small amplitude there. In contrast, the Es layer at higher altitude may be deeply modulated and appear as field aligned, since the amplitude of the gravity wave has increased greatly in comparison with the amplitude at lower altitude. The numerical results may be used to explain the midlatitude E region field-aligned irregularities observed by the Middle and Upper atmospheric (MU) radar.
BibTeX:
@article{Huang1996a,
  author = {Huang, Chao-Song and Kelley, Michael C.},
  title = {Numerical simulations of gravity wave modulation of midlatitude sporadic E layers},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {1996},
  volume = {101},
  number = {A11},
  pages = {24533-24543},
  url = {http://dx.doi.org/10.1029/96JA02327},
  doi = {10.1029/96JA02327}
}
Isham B, Hoz CL, Kohl H, Hagfors T, Leyser T and Rietveld M (1996), "Recent EISCAT heating results using chirped ISR", Journal of Atmospheric and Terrestrial Physics. Vol. 58, pp. 369-383.
Abstract: The chirp technique has recently become fully operational on the EISCAT UHF radar system and has been used for daytime observations of the HF-modified ionosphere over Ramfjordmoen in November 1992 and March 1993. During certain periods the UHF observations show a difference in the frequencies of the photoelectron-enhanced plasma line and the HF-enhanced plasma line (HFPL) similar to the one seen during chirp observations of heating at Arecibo. The frequency difference seen at EISCAT, however, varied dramatically with time and howetimes vanished completely, which was not the case at Arecibo. This frequency difference indicates that the HFPL source region is located several kilometres above the height where the linear Langmuir dispersion equation indicates a resonance should occur at the HF pump frequency. Simultaneous long-pulse measurements of the HFPL spectrum show a cascade-type structure in the HFPL spectra which, according to current theories, indicates that the HFPL must follow the Langmuir dispersion relation. This may be interpreted to mean that the HF-induced plasma waves are excited within plasma density depletions whenever the frequency difference is present. UHF observations also sometimes show a feature in the HF-modified plasma line spectrum which appears to be the same as that observed in an experiment performed at EISCAT in August 1986 by Isham et al. (1990). This new feature has been dubbed the “outshifted” line as it appears downshifted (upshifted) from the heating frequency in the downshifted (upshifted) plasma line spectrum. The magnitude of the shift is in the range of 100–300 kHz.
BibTeX:
@article{Isham1996,
  author = {B. Isham and C. La Hoz and H. Kohl and T. Hagfors and T.B. Leyser and M.T. Rietveld},
  title = {Recent EISCAT heating results using chirped ISR},
  journal = {Journal of Atmospheric and Terrestrial Physics},
  year = {1996},
  volume = {58},
  pages = {369-383},
  url = {http://www.sciencedirect.com/science/article/pii/0021916995000429},
  doi = {10.1016/0021-9169(95)00042-9}
}
Kildal P-S and Davis M (1996), "Characterisation of near-field focusing with application to low altitude beam focusing of the Arecibo tri-reflector system", IEE Proceedings on Microwaves, Antennas and Propagation. Vol. 143(4), pp. 284-292.
Abstract: Antennas are normally characterised in terms of their far field radiation patterns, directive gain and aperture efficiency. The paper describes how to characterise antennas that are focused in the near field, in terms of a focusing gain and a focusing efficiency. The paper also presents an algorithm from which the location of the near-field focus can be calculated directly from the aperture field of the antenna. The definitions and the algorithm are applied to an extensive numerical study of focusing of the beam of the Arecibo tri-reflector system at low altitudes. The focusing is obtained by displacing the feed, or the tertiary reflector, or both at the same time. Finally, an approximate formula is presented, from which results can be calculated easily at other frequencies and altitudes than those being computed
BibTeX:
@article{Kildal1996,
  author = {Kildal, P- S. and Davis, M.M.},
  title = {Characterisation of near-field focusing with application to low altitude beam focusing of the Arecibo tri-reflector system},
  journal = {IEE Proceedings on Microwaves, Antennas and Propagation},
  year = {1996},
  volume = {143},
  number = {4},
  pages = {284-292},
  url = {http://mr.crossref.org/iPage/?doi=10.1049%2Fip-map%3A19960388},
  doi = {10.1049/ip-map:19960388}
}
Mahajan K (1996), "Contributions of incoherent-scatter radar measurements at Arecibo for the improvement of IRI", Advances in Space Research. Vol. 18, pp. 131-140.
Abstract: In the years 1974 to 1977 the incoherent-scatter radar at Arecibo made high resolution measurements of electron density in time and altitude, under the I29 program. This program ran on monthly basis and each observing run was for about 36 hours, consisting of two daytime periods and the intervening night. Electron density was measured from 100 to 500 km with a single 24 vs pulse which provided an altitude resolution of 3.6 km. These measurements provided very accurate values of hmF2, h0.5, E-F valley parameters and topside Ne gradient thereby providing important inputs for the improvement of IRI. This paper gives a summary of these inputs.
BibTeX:
@article{Mahajan1996,
  author = {Mahajan, K},
  title = {Contributions of incoherent-scatter radar measurements at Arecibo for the improvement of IRI},
  journal = {Advances in Space Research},
  year = {1996},
  volume = {18},
  pages = {131-140},
  url = {http://dx.doi.org/10.1016/0273-1177(95)00913-2},
  doi = {10.1016/0273-1177(95)00913-2}
}
Mathews JD (1996), "The dynamics of ion layer generation in the 80–150 km altitude region at low and mid-latitudes", Journal of Atmospheric and Terrestrial Physics . Vol. 58(6), pp. 673 - 682.
Abstract: The association of sporadic ion and sporadic sodium layers in the low-latitude, 90–100 km altitude region suggests that we must look beyond the windshear theory for details of the formation mechanism of sporadic layers in the 80–150 km altitude region. We present evidence, including specific 85–105 km results from the AIDA-89 and the ALOHA-90 campaigns, that 80–150 km altitude sporadic layers—including sporadic sodium layers—are generated in a complex interplay of tidal and acoustic-gravity wave (AGW) dynamics with temperature-dependent chemistry where wave-produced temperature variations are both adiabatic and dissipative or turbulent (non-reversible) in origin. We suggest that layering processes are best studied with an instrument cluster that includes sodium and iron lidars, MST radar (turbulence), incoherent scatter radar (electron concentration and winds), meteor radar techniques (winds), passive optical/IR imaging techniques, and appropriate rocket payloads to study a significant volume of the 80–150 km altitude region. We introduce the concept of volumtric radar and lidar techniques.
BibTeX:
@article{Mathews1996,
  author = {John D. Mathews},
  title = {The dynamics of ion layer generation in the 80–150 km altitude region at low and mid-latitudes},
  journal = {Journal of Atmospheric and Terrestrial Physics },
  year = {1996},
  volume = {58},
  number = {6},
  pages = {673 - 682},
  note = {Ionosphere-Middle and Lower Atmosphere Interactions },
  url = {http://www.sciencedirect.com/science/article/pii/0021916995000666},
  doi = {10.1016/0021-9169(95)00066-6}
}
Miller N, Grebowsky J, Hoegy W and Mahajan K (1996), "A comparison of ionization densities determined from spacecraft and incoherent scatter radar data", Journal of Atmospheric and Terrestrial Physics . Vol. 58(15), pp. 1735 - 1740.
Abstract: By comparing direct measurements taken from onboard Atmosphere Explorer spacecraft (AE), in eccentric orbit, with incoherent scatter radar (ISR) measurements taken from the ground, we illustrate both the merits and the difficulties involved in such comparisons. Five altitude profiles of ionization determined from AE, in near coincidence with ground stations making ISR measurements, compared favorably with the ISR data so long as the Æ measurements were properly analyzed for the effects of variations in latitude and solar zenith angle along the spacecraft orbit.
BibTeX:
@article{Miller1996,
  author = {N.J. Miller and J.M. Grebowsky and W.R. Hoegy and K.K. Mahajan},
  title = {A comparison of ionization densities determined from spacecraft and incoherent scatter radar data},
  journal = {Journal of Atmospheric and Terrestrial Physics },
  year = {1996},
  volume = {58},
  number = {15},
  pages = {1735 - 1740},
  url = {http://www.sciencedirect.com/science/article/pii/0021916995002006},
  doi = {10.1016/0021-9169(95)00200-6}
}
Mitra A (1996), "Feasible groundbased atmospheric and flux measurements by developing countries in support of satellite data", Advances in Space Research . Vol. 17(8), pp. 17-26.
Abstract: To allow increasing participation of developing countries in global change studies, ground based measurement systems which can be easily comissioned and provide support to satellite observations so as to fit into global mapping need to be chosen carefully. Those relating to atmospheric parameters (greenhouse gas concentrations, emission fluxes, transport properties, etc.) are discussed here. The simplest and of most immediate interest relate to sources and sinks of CH4 (primarily from rice paddy fields, animals, wetlands) and N2O (soils, oceans). Measurement techniques and inter-country campaign plans are discussed. There are also important possibilities of using the same technique for measurements of emissions from biomass burning alongwith ozone measurements coupled with survey of biomass burning areas from satellites. Another major area concerns the proposed ITYO programme (International Troposheric Ozone Year), for which, apart from balloon ozone ascents, use of UV-B radiometry at selected wavelengths is considered. The third area discussed concerns measurements of atmospheric aerosols using Multi-wavelength Radiometer (MWR). In addition, in the last few years, a number of advanced groundlevel systems have been installed at low latitudes, which, if made available widely to developing country scientists, and their participation supported financially, could provide a major opportunity for world class research. These include: the MST radar at Tirupati (India) Chung-Li (Taiwan) and Arecibo, Puerto Rico; the Lidars at Thumba and at Natal, Brazil; and the Laser Heterodyning System and mm-wave radiospectrometer at Delhi.
BibTeX:
@article{Mitra1996,
  author = {A.P. Mitra},
  title = {Feasible groundbased atmospheric and flux measurements by developing countries in support of satellite data},
  journal = {Advances in Space Research },
  year = {1996},
  volume = {17},
  number = {8},
  pages = {17-26},
  url = {http://www.sciencedirect.com/science/article/pii/027311779500655X},
  doi = {10.1016/0273-1177(95)00655-X}
}
Pandey VK, Sethi NK and Mahajan KK (1996), "Comparison of IRI topside electron density profile with Arecibo incoherent scatter measurements", Advances in Space Research. Vol. 18(6), pp. 289-292.
Abstract: Midday and Midnight topside electron density profiles measured with the incoherent scatter radar at Arecibo (magn.dip 50°) are compared with the IRI-90. It is found that, in general, IRI overestimates electron densities. Similar results have earlier been reported from Millstone Hill (magn.dip 72°).
BibTeX:
@article{Pandey1996,
  author = {Pandey, V K and Sethi, N K and Mahajan, K K},
  title = {Comparison of IRI topside electron density profile with Arecibo incoherent scatter measurements},
  journal = {Advances in Space Research},
  year = {1996},
  volume = {18},
  number = {6},
  pages = {289-292},
  url = {http://dx.doi.org/10.1016/0273-1177(95)00938-8},
  doi = {10.1016/0273-1177(95)00938-8}
}
Pandey VK and Sethi NK (1996), "Comparison of hmF2 and midday bottomside electron density profile obtained from IRI and incoherent scatter measurements", Advances in Space Research. Vol. 18(6), pp. 33-37.
Abstract: About 2000 electron density height profiles observed with the Arecibo (magn.dip 50°) incoherent scatter radar are used to compare the diurnal and seasonal variations of hmF2 with the IRI-90. A good agreement is seen for the median values. The midday bottomside profiles normalized to the peak density are compared with IRI-90 for each season and it is found that IRI overestimates the electron density distribution in the region 100 km below the F2 peak for equinox and summer but matches well during winter.
BibTeX:
@article{Pandey1996a,
  author = {Pandey, V K and Sethi, N K},
  title = {Comparison of hmF2 and midday bottomside electron density profile obtained from IRI and incoherent scatter measurements},
  journal = {Advances in Space Research},
  year = {1996},
  volume = {18},
  number = {6},
  pages = {33-37},
  url = {http://dx.doi.org/10.1016/0273-1177(95)00895-0},
  doi = {10.1016/0273-1177(95)00895-0}
}
Sethi N, Goel M and Pandey V (1996), "Deriving main LAY parameters from Incoherent Scatter measurements and their comparisons with IRI-90", Advances in Space Research. Vol. 18(6), pp. 141-144.
Abstract: Using high resolution electron density (Ne) profiles from Incoherent Scatter (I.S.) measurements at Arecibo, geometric parameters (transition height, scale height) of 4 LAY functions are determined. The median values of the above parameters are obtained for each hour during different seasons and compared with main LAY parameters obtained from IRI-90. It is observed that during all the seasons the transition height parameter of the F2 layer derived from observed profiles agrees well with the parameter obtained from IRI during daytime only, while for nighttime large departures are observed for all seasons. Large seasonal variability is also found in the principal scale parameter related to thickness of F2 layer. The difference between those in observed profiles compared to IRI varies from 38 km to 45 km.
BibTeX:
@article{Sethi1996,
  author = {N.K. Sethi and M.K. Goel and V.K. Pandey},
  title = {Deriving main LAY parameters from Incoherent Scatter measurements and their comparisons with IRI-90},
  journal = {Advances in Space Research},
  year = {1996},
  volume = {18},
  number = {6},
  pages = {141-144},
  url = {http://dx.doi.org/10.1016/0273-1177(95)00914-0},
  doi = {10.1016/0273-1177(95)00914-0}
}
Sulzer MP and Gonzalez SA (1996), "Simultaneous measurements of O+ and H+ temperatures in the topside ionosphere over Arecibo", Geophysical Research Letters. Vol. 23(22), pp. 3235-3238.
Abstract: We have measured both proton (TH+) and oxygen ion (TO+) temperatures simultaneously from spectra obtained in the lower topside ionosphere using the Arecibo incoherent scatter radar (ISR). This is the first time that two ion temperatures and three ion compositions have been measured from the same IS spectrum, and, as far as we know, one of the first measurements of both ion temperatures in the ionosphere.First we describe our spectral-domain analysis technique, emphasizing the ability to determine goodness of fit, which allows of the need for and effect of including a parameter to be numerically evaluated. We then show that common TH+ and TO+ allow insufficient freedom, and that separate temperatures are sufficient.A small negative bias in [He+] parameter is removed when the second temperature is allowed to be free while the H+ fraction is not significantly affected. We also show that the measurement cannot be made at altitudes where little O+ is present. The difference between TH+ and TO+ is zero (or at least very small) during the night, and rises to several hundred degrees at about 500 km shortly after sunrise. During the middle of the day the temperature difference declines (presumably due to higher densities) and then rises again before sunset.
BibTeX:
@article{Sulzer1996,
  author = {Sulzer, Michael P. and Gonzalez, Sixto A.},
  title = {Simultaneous measurements of O+ and H+ temperatures in the topside ionosphere over Arecibo},
  journal = {Geophysical Research Letters},
  year = {1996},
  volume = {23},
  number = {22},
  pages = {3235-3238},
  url = {http://dx.doi.org/10.1029/96GL02926},
  doi = {10.1029/96GL02926}
}
Rottger J and Tsuda T (1995), "Studies of the Polar Middle and Lower Atmosphere by an MST Radar on Svalbard", Journal of geomagnetism and geoelectricity. Vol. 47(9), pp. 929-942.
Abstract: This paper describes scientific subjects important in the middle atmosphere in the polar region, considering the effects of phenomena unique to the high latitudes as well as the coupling processes between the neutral and ionized atmosphere. We are particularly pointing out the relevant application of an MST (mesosphere-stratosphere-troposphere) radar for observations of middle and lower atmospheric structure and dynamics. We briefly summarize fundamental techniques of the MST radar. Then, we survey phenomena that are exclusively detected in the polar atmosphere, such as precipitation of high energy particles, aurora) electrojet, stratospheric sudden warming, the polar vortex or a polar night-jet, PSC (polar stratospheric cloud) associated with ozone depletion and PMSE (polar summer mesospheric echoes), related to NLC (noctilucent clouds). Among these phenomena there are certain topics that need to be studied with an MST radar in addition to the multitude of other complementary experiments which are already applied for these studies in the Arctic and Antarctic. Finally, we discuss a realization of an MST radar operated on 50 MHz, which should be established in conjunction with the Svalbard incoherent scatter radar operated on 500 MHz.
BibTeX:
@article{1995929,
  author = {Jurgen Rottger and Toshitaka Tsuda},
  title = {Studies of the Polar Middle and Lower Atmosphere by an MST Radar on Svalbard},
  journal = {Journal of geomagnetism and geoelectricity},
  year = {1995},
  volume = {47},
  number = {9},
  pages = {929-942},
  url = {https://www.jstage.jst.go.jp/article/jgg1949/47/9/47_9_929/_article},
  doi = {10.5636/jgg.47.929}
}
Bernhardt PA, Ganguli G, Kelley MC and Swartz WE (1995), "Enhanced radar backscatter from space shuttle exhaust in the ionosphere", Journal of Geophysical Research: Space Physics. Vol. 100(A12), pp. 23811-23818.
Abstract: Enhancements in the backscatter from the 430-MHz radar at Arecibo were recorded during the Spacelab 2 mission when the space shuttle orbital maneuver system (OMS) engines were fired in the ionosphere. The modifications in the backscatter could have been the result of (1) compression of the electrons to produce higher densities, (2) generation of ion acoustic waves, (3) variations in the electron to ion temperature ratio, (4) enhanced scatter cross section by charging of ice particles in the exhaust, or (5) excitation of dust acoustic waves. Rapid cooling and condensation of the exhaust are important in determining the scattering properties of the modified ionosphere. A dusty plasma is formed when electrons are attached to ice particles in the exhaust plume. The calculated neutral temperature inside the exhaust plume is 120 K. Charge exchange between ambient O+ and the cold exhaust molecules yields low-temperature ion beams that excite weakly damped, ion acoustic waves. The enhanced radar echoes are probably the result of scatter from these waves, but the effects of the dusty plasma may be important. During future experiments, the space shuttle will fire the OMS engines over radars located at Arecibo, Puerto Rico; Jicarmarca, Peru; or Kwajalein, Marshall Islands. Measurements of the spectra from these radars will provide the means to distinguish between the various backscatter processes.
BibTeX:
@article{Bernhardt1995,
  author = {Bernhardt, P. A. and Ganguli, G. and Kelley, M. C. and Swartz, W. E.},
  title = {Enhanced radar backscatter from space shuttle exhaust in the ionosphere},
  journal = {Journal of Geophysical Research: Space Physics},
  year = {1995},
  volume = {100},
  number = {A12},
  pages = {23811-23818},
  url = {http://dx.doi.org/10.1029/95JA02836},
  doi = {10.1029/95JA02836}
}
Bernhardt PA, Siefring CL, Rodriguez P, Haas DG, Baumback MM, Romero HA, Solin DA, Djuth FT, Duncan LM, Hunton DE, Pollock CJ, Sulzer MP, Tepley CA, Wagner LS and Goldstein JA (1995), "The Ionospheric Focused Heating experiment", Journal of Geophysical Research. Vol. 100, pp. 17331-17346.
Abstract: The Ionospheric Focused Heating rocket was launched on May 30, 1992. The sounding rocket carried an instrument and chemical payload along a trajectory that crossed the intersection of the beams from the 430-MHz incoherent scatter radar and the 5.1-MHz high-power radio wave facility near Arecibo. The release of 30 kg of CF3Br into the F region at 285 km altitude produced an ionospheric hole that acted like a convergent lens to focus the HF transmissions. The power density inside the radio beam was raised by 12 dB immediately after the release. A wide range of new processes were recorded by in situ and ground-based instruments. Measurements by instruments flying through the modified ionosphere show small-scale microcavities (<1 m) and downshifted electron plasma (Langmuir) waves inside the artificial cavity, electron density spikes at the edge of the cavity, and Langmuir waves coincident with ion gyroradius (4 m) cavities near the radio wave reflection altitude. The Arecibo incoherent scatter radar showed 20 dB or greater enhancements in ion acoustic and Langmuir wave turbulence after the 5.1-MHz radio beam was focused by the artificial lens. Enhancements in airglow from chemical reactions and, possibly, electron acceleration were recorded with optical instruments. The Ionospheric Focused Heating experiment verified some of the preflight predictions and demonstrated the value of active experiments that combine high-power radio waves with chemical releases.
BibTeX:
@article{Bernhardt1995a,
  author = {Bernhardt, P A and Siefring, C L and Rodriguez, P and Haas, D G and Baumback, M M and Romero, H A and Solin, D A and Djuth, F T and Duncan, L M and Hunton, D E and Pollock, C J and Sulzer, M P and Tepley, C A and Wagner, L S and Goldstein, J A},
  title = {The Ionospheric Focused Heating experiment},
  journal = {Journal of Geophysical Research},
  year = {1995},
  volume = {100},
  pages = {17331-17346},
  url = {http://dx.doi.org/10.1029/94JA01887},
  doi = {10.1029/94JA01887}
}
Buonsanto M and Holt J (1995), "Measurements of gradients in ionospheric parameters with a new nine-position experiment at Millstone Hill", Journal of Atmospheric and Terrestrial Physics . Vol. 57(6), pp. 705-717.
Abstract: A new nine-position experiment is now routinely carried out with the Millstone Hill incoherent scatter radars which allows estimation of spatial gradients in the measured ionospheric scalar parameters Ne, Te, and Ti, and in the components of the ion velocity vector vi. Use of this technique results in improved estimates of basic and derived parameters from incoherent scatter data at times of significant gradients. We detail the data analysis method and present the first results from this new experiment. The gradients in Ne and in the components of vi are used to compute the motion term in the ionospheric F region continuity equation v · (Nv), which is then combined with DN/Dt to estimate the O+ recombination rate betha at night. Meridional neutral winds Umer are computed from the field-aligned ion velocity vpar and a calculation of the O+ diffusion velocity vd, and it is found that horizontal gradients in the ion velocity field at times significantly affect the calculation of the neutral winds.
BibTeX:
@article{Buonsanto1995,
  author = {M.J. Buonsanto and J.M. Holt},
  title = {Measurements of gradients in ionospheric parameters with a new nine-position experiment at Millstone Hill},
  journal = {Journal of Atmospheric and Terrestrial Physics },
  year = {1995},
  volume = {57},
  number = {6},
  pages = {705-717},
  url = {http://www.sciencedirect.com/science/article/pii/002191699400047R},
  doi = {10.1016/0021-9169(94)00047-R}
}
Cho JYN and Morley RL (1995), "PMSE dependence on long-period vertical motions", Geophysical Research Letters. Vol. 22(10), pp. 1197-1200.
Abstract: We analyze the temporal relationship between PMSE (polar mesosphere summer echoes) and long-period vertical motions using the Poker Flat, Alaska radar data. The results show that the vertical velocity leads PMSE by 90° to 180° with a possible upward trend in phase with increasing frequency. We show that this is consistent with the current PMSE theories which depend primarily upon the presence of charged ice aerosols for the enhancement of radar scatter.
BibTeX:
@article{Cho1995,
  author = {Cho, John Y. N. and Morley, Rebecca L.},
  title = {PMSE dependence on long-period vertical motions},
  journal = {Geophysical Research Letters},
  year = {1995},
  volume = {22},
  number = {10},
  pages = {1197-1200},
  url = {http://dx.doi.org/10.1029/95GL01010},
  doi = {10.1029/95GL01010}
}
Cho JYN (1995), "Inertio-gravity wave parameter estimation from cross-spectral analysis", Journal of Geophysical Research: Atmospheres. Vol. 100(D9), pp. 18727-18737.