Multi-Metal Resonance Lidars


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Multi-Metal Resonance Lidars

The existence of a permanent metal layers in the MLT region were recognized with the airglow instruments. These metals are attributed to the meteoroid ablation processes, and originate from the cosmic dust particles. The main sources of this dust are collisions between asteroids and the sublimation of comets as they approach towards the Sun during their orbital motion. It is interesting to mention that even though meteor showers like Leonids, Parseids or Geminids are more popular and display spectacular trails visible by the naked eye (Please check the link: https://www.amsmeteors.org/photos), majority of the mass flux in the MLT region is deposited through continuous input of sporadic meteoroids. These metals act as tracers for investigating dynamics and energetics of the MLT region, and in this regards resonance lidars play a significant role in advancing our knowledge about this part of the atmosphere.

Na/Ca+ Lidar Instrument Description at AO

Figure 3.0 YAG beam at 532 nm in the lidar lab. The pulse energy per pulse ~ 600 mJ and laser divergence ~ 0.5 mr.

A brief overview of the YAG lasers and the associated techniques for inferring MLT Na concentrations and Ca+ ions is discussed in this section. The YAG lasers operate at 50 Hz and the fundamental at 1064 Å is frequency doubled to 532 nm (Figure 3). This pumps a dye laser, which can be tuned to Na resonance wavelength ~ 589 nm. To perform UV measurements at 393nm (resonance wavelength of Ca+), sum frequency technique is employed as illustrated in the schematics (Figure 4).

Schematics - UV Photon Generation

Figure 4.0 Schematics showing the principle of UV photon generation at AO. The backscattered photons are collected using 0.8 m Cassegrain type telescope coupled to Photo-multiplier tube using an optical fiber.

Rayleigh Lidar

The frequency doubled output from the YAG laser is sometimes sent directly to the atmosphere for inferring the atmospheric temperature profile between 30 – 85 km altitude regions. This when combined with the K Doppler resonance lidar measurements of mesospheric temperatures can extend the neutral temperature profile to 100 km. Only a few measurements have been made in this mode when the dye laser is not being pumped by the 532 nm YAG beam. In the future, it would be good to have an independent Rayleigh system to enhance our capabilities and scientific outcomes.


Observations/Results

The above instruments have contributed to the scientific growth and resulted in several collaborations. Some examples are listed as follows: Ion- Neutral Interactions Combined observations of electron concentrations and resonance lidars have yielded significant results. One of the highly debated topic is the occurrence of the thermospheric metals. Role of ion-neutralization have been invoked to explain the presence of thermospheric neutral iron atoms at high latitudes. However, at Arecibo no such link is observed at altitudes above meteoric ablation zone. An example is shown in the Figure 5:

Figure 5 Potassium and sodium lidar data (left and middle panels), and electron concentrations obtained using Incoherent Scatter Radar data (right panel) illustrating different descent rate of the neutral and ionized layers at thermospheric altitudes. [Adapted from Raizada et al., GRL, 2015a].

Some examples related to this subject can be found in the following publications:

  • Tepley, et al, "First simultaneous observations of Ca+, K, and electron density using lidar and incoherent scatter radar at Arecibo" Geophys. Res. Lett., Vol. 30, No.1, 10.1029/2002GL015927, 2003
  • Raizada, and Tepley , "Seasonal variation of mesospheric iron layers at Arecibo: First results from low-latitudes" Geophys. Res. Lett., Vol. 30, No. 2, 1082, doi:10.1029/2002GL016537, 2003.
  • Raizada et al, “Characteristics of neutral Calcium, Ca+ and their relationship to sporadic Ion/Electron Layers at Arecibo”, Geophys. Res. Letts., Vol. 38, l09103, doi:10.1029/2011GL047327, 2011.
  • Raizada, et al., “Summer to winter variability in mesospheric calcium ion distribution and its dependence on Sporadic E at Arecibo”, J. Geophys. Res., Vol. 117, A02303, doi:10.1029/2011JA016953, 2012.
  • Delgado, et al, Sporadic metal atom and ion layers and their connection to chemistry and thermal structure in the mesopause region at Arecibo, J. Atmos. And Solar Terrs. Phys., doi:10.1016/j.jastp.2011.09.004, 2012.
  • Raizada, et al., “First simultaneous measurements of Na and K thermospheric layers along with TILs from Arecibo”, Geophys. Res. Lett., 42, doi:10.1002/2015GL066714, 2015a.
  • Raizada, et al., “Dependence of mesospheric Na and Fe distributions on electron density at Arecibo”, Earth, Planet and Space, 67:146, DOI 10.1186/s40623-015-0322-z, 2015b. Future efforts should focus on combining calcium ion, ionosonde and other metal neutral data sets to understand the generation, occurrence frequency of such events at different latitudes.
Ion-Transport Processes

The processes associated with transfer of energy from either high or low or equatorial latitudes are still unresolved. Satellites provide excellent spatial coverage but have restrictions in providing insights into temporal evolution of structures at a high resolution. Such processes can be best understood by combining ground based instruments and ICON satellite mission data sets. Having an ISR at Arecibo along with direct measurements of meteoric metal ions using resonance lidars have provided new insights into the F-region valley dynamics that appears to be unique to AO location [Raizada et al., GRL, 2020a]. Future endeavors should also focus on the development of new solid state transmitter to be used in Calcium ion measurements using a lidar as it opens up new dimensions and promises new discoveries with narrow-bandwidth of such lasers.

A recent study presented at the American Geophysical Union (AGU) Fall meeting in December 2020 discussed the significance of Arecibo location and the coupling between equatorial and mid-latitudes [Raizada et al., 2020b]. This investigation showed the first observational evidence of the metals ions transport via electrodynamical processes that resulted in appearance of metal ion layers in the F-region valley as shown in the Figure 6. However, the collapse of Arecibo ISR limits such studies, and an advanced system as proposed promises new and novel contributions in this area.

Figure 6 Range Time plot of electron concentration obtained using ISR over Arecibo (upper), and calcium ion distribution from the resonance lidar for three consecutive nights (lower panels). It shows the occurrence of Ca+ layers in the F-region valley, [Raizada, et al. (2020), Geophysical Research Letters, 47, e2020GL087113. https://doi.org/10.1029/2020GL087113].


Collaborative Work

Some selected publications illustrating the collaborative work are listed below:

  • Cai, et al, Investigation on the distinct nocturnal secondary sodium layer behavior above 95 km in winter and summer over Logan, UT (41.7° N, 112° W) and Arecibo Observatory, PR (18.3° N, 67° W), J. Geophys. Res., 10.1029/2019JA026746, 2019.
  • Plane et al., A new model of meteoric calcium in the mesosphere and lower thermosphere, Atmos. Chem. Phys., 18, 14799–14811, 2018.
  • Mathews, et al, High-altitude radar and optical meteors and meteoroid sputtering as a source for lower thermospheric metals, In the Proceeding for 32nd USRI GASS, Montreal, 19-26 August, 2017.
  • Yue, et al, Simultaneous and common-volume lidar observations of K/Na layers and temperature at Arecibo Observatory (18°N, 67°W), J. Geophys. Res. Atmos.,121, 8038– 8054, doi:10.1002/2015JD024494, 2016.
  • Sarkhel, et al, A case study on occurrence of an unusual structure in the sodium layer over Gadanki, India. Earth, Planet & Space, doi:10.1186/s40623-015-0183-5, 2015.
  • Sarkhel et al., J. Geophys. Res., Vol. 117, A10301, doi:10.1029/2012JA017891, 2012.
  • X. Cai, T. Yuan, J. Eccles, S. Raizada, Investigation on the distinct nocturnal secondary sodium layer behavior above 95 km in winter and summer over Logan, UT (41.7° N, 112° W) and Arecibo Observatory, PR (18.3° N, 67° W), J. Geophys. Res., 10.1029/2019JA026746, 2019. Plane J. M. C., W. Feng, J. C. G. Martin, M. Gerding, S. Raizada, A new model of meteoric calcium in the mesosphere and lower thermosphere, Atmos. Chem. Phys., 18, 14799–14811, 2018.
  • J. D. Mathews, B. Gao, V. Kesaraju, S. Raizada, High-altitude radar and optical meteors and meteoroid sputtering as a source for lower thermospheric metals, In the Proceeding for 32nd USRI GASS, Montreal, 19-26 August, 2017.
  • Yue, X., Q. Zhou, F. Yi, J. Friedman, S. Raizada, and C. Tepley (2016), Simultaneous and common-volume lidar observations of K/Na layers and temperature at Arecibo Observatory (18°N, 67°W), J. Geophys. Res. Atmos.,121, 8038–8054, doi:10.1002/2015JD024494.
  • S. Sarkhel, J. D. Mathews, S. Raizada, R Sekar, D. Chakrabarty, A. Guharay, Robert B. Kerr, Geetha Ramkumar, S. Sridharan, Qian Wu, Martin G. Mlynczak, and James M. Russell III (2015), A case study on occurrence of an unusual structure in the sodium layer over Gadanki, India. Earth, Planet & Space, doi:10.1186/s40623-015-0183-5. S. Sarkhel, S. Raizada, J. D. Mathews, S. Smith, C. A. Tepley, Francisco Rivera, S. A. Gonzalez, Identification of large scale billows-like structure in the neutral Na layer over Arecibo, , J. Geophys. Res., Vol. 117, A10301, doi:10.1029/2012JA017891, 2012.

Contact Person

Dr. Shikha Raizada AO Observation Scientist
Space & Atmospheric Sciences Department
Arecibo Observatory
shikha@naic.edu, shikha.raizada@ucf.edu