Update of PWG activities, with emphasis on Saturn's lightning

Philippe Zarka
LOFAR TKP Meeting, Amsterdam, June 2011

Transcript

1. (Tentative) Observations of Saturn’s Lightning P. Zarka & the Planets WG June 2011 TKP meeting, Amsterdam
2. Flux observed about 10 MHz for Saturn’s lightning (SED – in yellow) and the two possible interpretations (A) and (B). + test for exoplanet searches
3. The data : Incoherent sum of 22 CS & RS stations (Stokes I only) 81 µsec, 195/16 kHz Pre-processing = integration over channels 1-14 = 170 kHz 8 hours of continuous observation, 24 MHz On, 24 MHz Off (spatial) 17/12/2010 03:00 - 11:00 UT (Off = arbitrary pointing) 18/12/2010 03:00 - 11:00 UT (Off = PSR 1133+16)
4. 24 MHz bandwidth distributed over the range 15-75 MHz with ~20 bands x 1.2 MHz separated by gaps of 1.8 MHz
5. 17/12/2010 18/12/2010 03:00 11:00 Dynamic spectrum pre-integrated over 16 msec → strong pollution at LF + HF (saturation?), increases ~07:00 UT
6. Observed spectrum
8. 17/12/2010 - SubBand 4 - last 10 pixels of each 1 sec block
9. Fast oscillations at 100 & Nx293.5 Hz up to 5 kHz, most intense at 587 Hz
10. 17/12/2010 - SubBand 0 (=15 MHz)
11. 17/12/2010 - SubBand 10
12. 17/12/2010 - SubBand 30
13. 17/12/2010 - SubBand 50
14. Baseline jumps, uncorrelated between SubBands or Channels
15. 17/12/2010 - SubBand 90
16. 17/12/2010 - SubBands 10-124
17. 17/12/2010 - SubBands 10-124 18/12/2010 - SubBands 10-124
18. 17/12/2010 - SubBands 60-100
19. Spectral integration + peak detection ON / OFF → noise only Processing: - pre-integration over 4 msec (1 sigma = 100-500 Jy) - clean RFI spikes (400 msec sliding window, 5 sigmas level) - data/running_median(1 sec) -1 - statistics of avg + stdev per sec → discard those ≠ theoretical (1/sqrt(14x50) ~ 0.038) - spikes detection at 3 sigmas level, On vs Off statistics
20. 17/12/2010 - SubBand 50 17/12/2010 - SubBand 60
21. 17/12/2010 - SubBand 50 17/12/2010 - SubBand 60
22. 17/12/2010 - SubBand 50 17/12/2010 - SubBand 60
23. 17/12/2010 - SubBand 50 17/12/2010 - SubBand 60
24. 17/12/2010 - SubBand 50 17/12/2010 - SubBand 60
25. 17/12/2010
26. UIOWA 20110627 2010-12-17 (351) 00:00 2010-12-17 (351) 16:00 32,26 207,70 -0,06 19,66 32,26 31,72 308,41 -0,06 19,70 31,72 31,17 49,09 -0,06 19,75 31,17 30,59 149,74 -0,06 19,79 30,59 30,01 250,37 -0,06 19,84 30,01 29,40 350,97 -0,06 19,89 29,40 00:00 03:00 06:00 09:00 12:00 15:00 Orbit 142 R S Lon Lat LT L 2, 4, 6, 8, 10, 12, 14, 16, Frequency (Hz) 0, 5, 10, 15, 20, dB Above Background (7%) Earth ~ Cassini - 3.7h
27. 18/12/2010
28. UIOWA 20110627 2010-12-18 (352) 00:00 2010-12-18 (352) 16:00 27,47 292,56 -0,06 20,06 27,47 26,78 33,01 -0,06 20,11 26,78 26,08 133,41 -0,07 20,18 26,08 25,35 233,76 -0,07 20,24 25,35 24,60 334,05 -0,07 20,32 24,60 23,83 74,27 -0,07 20,39 23,83 00:00 03:00 06:00 09:00 12:00 15:00 Orbit 142 R S Lon Lat LT L 2, 4, 6, 8, 10, 12, 14, 16, Frequency (Hz) 0, 5, 10, 15, 20, dB Above Background (7%) Earth ~ Cassini - 3.9h
29. → Possible marginal detection on 2010/12/18, tbc → Correlate with Cassini data → Analyze TBB data (S. ter Veen) → Re-analyze 2010/04/08
30. PSR 1133 in Off beam on 2010/12/18 (no processing)
31. No detection before processing PSR 1133 in Off beam on 2010/12/18 (no processing)
32. PSR 1133 in Off beam on 2010/12/18 (after processing)
33. PSR 1133 in Off beam on 2010/12/18 (no processing)
36. UIOWA 20110627 2011-06-20 (171) 00:00 2011-06-27 (178) 00:00 13,37 210,26 -0,12 10,91 13,37 27,57 359,88 0,08 13,04 27,57 36,29 170,44 0,15 13,77 36,29 41,79 344,69 0,19 14,25 41,79 2011-06-20 2011-06-22 2011-06-24 2011-06-26 Orbit 149 R S Lon Lat LT L 2, 4, 6, 8, 10, 12, 14, 16, Frequency (Hz) 0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0 dB Above Background (7%) + redo new Saturn observations (storm still active)
37. Lessons learned → No blind sum (coherent or incoherent) on many stations → (near) real-time test individual station responses prior to observation ? (cf. pulsars, J. Hessels) → Real-time flagging of polluted station signals ( → Perform sums in sub-groups of data ) → Perform coherent TAB (n^2 more sensitive, superterp first)