Intro

• a 63 second periodic pulse around 27 MHz
• 2.4 MHz ripple across the band that turned on suddenly.
  
• dropouts in pol B
  

The data:

    The  first plots shows the total power (20 to 80 MHz) vs time for then entire day (.ps) (.pdf)

• Black is polA, red is pol B
• The points are sampled every .25 seconds.
• The green lines show the data used to look at the 63 second period pulses.
• The blue line has the start of the ripples
• Both polA and B increase when the ripples start (polA more than pol B).
• The negative going spikes in pol B are the pol B dropouts.
• the blowup plots show that they are not resolved in the .25 sec spectra.
• Looking at the dynamic spectra, the dropouts are across the entire band.
• They are not seen in polA.

• Page 1: 63 second pulses total and pol B dropouts
  
• Top: 45 minutes of total power vs time using 25 to 30 MHz.
  
• the positive going spikes are the 63 sec  pulse.
• The large negative going pulses (pol B) are the pol B dropouts. they are about 2 counts.
  
• Middle: total power spectrum (magnitude).
• 45 minutes of data (at .25 sec sampling) was transformed to get the frequency of the pulses.
• There is a comb present.
  
• the 29th harmonic is .47528 hz , so the fundamental is (.47528/30)= .01584 Hz  or 63.1 seconds.
• bottom: fold the total power vs time data at 63.1 seconds
  
• Black is polA, red is pol B.
• blue is a single period before folding.
• The power goes down (below the mean value)  for about 3 seconds and then goes up (above the mean value) for 2 seconds.
• The image shows the dynamic spectra for these 45 minutes (.gif)
• The pulses are occurring around 27 MHz.
• the lower frame is pol B. The vertical black strips are the pol B dropouts.
  
• The power dropout before the pulse would normally be caused by out of band compression.
  
• If the signal was compressed for 3 seconds, we should also see a dark line across the entire band (which we don't see).
• This may be an instrumental affect.
• Page 2: spectral ripples.
• Top: total power vs time when ripples start
• black is polA, red is pol B
• the ripples turn on around 13.587. Both polA and pol B power increase at the turn on.
• the negative red going spikes are the pol B dropouts.
• 2nd: total power vs time blowup at ripple turnon.
• the +'s are the .25 second samples
• the polA spike comes 1 sample before the pol B spike.
• 3rd: spectral density plots at the ripple turn on.
• black is before the start
• red is at the start
• There is a very strong ripple that goes from 60 to 85 MHz. It goes down on the next .25 second sample
• We saw a similar oscillation at ripple turn on back on 27jan22
  
• green is after the start.
• bottom: average acf of the spectra
• The acf was computed for each spectra (starting after the turn on) and then averaged
• The plot shows the acf vs the lag delay (in usecs).
• There is a spike at .405 microseconds. This would be a 1/.405 2.47 MHz ripple.
• We saw a similar lag delay in the 27jan22 data.
  

• dynamic spectra at ripple turnon (.gif)
• Top frame:polA
• bottom frame pol B
• the ripples turn on at 13.587.
• The bright vertical line 65 to 80 MHz is the strong oscillation at turnon.
• acf vs lag at ripple turn on (.gif)
• top  is polA
• bottom is pol B
• the vertical scale in lag delay in usecs
• The horizontal line at .4 usecs is the ripple lag delay (stronger in polA).
  

SUMMARY:

• A 63.1 second periodic pulse around 27.5 MHz is seen in the data
• there is a 3 second total power decrease followed by a 2 second increase
• Since the decrease is not seen across the entire freq band, it is probably not out of band compression.
• Dropouts were seen in pol B
• they cover the entire frequency band
• they are not resolved in the .25 second samples.
• they do not occur in polA
• 2.4 MHz ripples
• Turn on fast (1 sample)
• At turn on there is a large oscillation (at the 2.4 MHz ripple period) across a portion of the band.
• The large oscillation occurs 1 time sample (.25 sec) later in pol B.
  
• this has been seen in multiple days.
  

processing: x101/220202/callisto_ripple_dropouts.pro

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