1. 1 2008 Corsica TLE Workshop Fast 2-D Photometric Imaging of Elves June 24, 2008 Robert T Newsome* Umran S Inan Space, Telecommunications, and Radioscience Laboratory Electrical Engineering Department Stanford University, Stanford, California 94305 http://www-star.stanford.edu/~vlf/

2. 2 Overview  Introduction to the PIPER instrument  Imaging with PIPER  2007 Observation Campaign  TLE(s) at 06:01:46 UT on July 10, 2007  Video camera data  PIPER data  Comparison  The elve at 06:01:46 UT on July 10, 2007  More elves from July 10, 2007  Summary

3. 3 Introduction to PIPER  Photometric “camera”, with  High sampling rates (up to 25k samples/sec)  High optical sensitivity  Traded off against spatial resolution, BUT  Some spatial resolution recovered using multi-anode photometers (vs. conventional single-anode photometers)  Four Hamamatsu R5900U-20-L16 16-anode photometers  18 degree fields of view  Operate in pairs  Turned at right angles  Augmented w/ video camera (not shown)

4. 4 Introduction to PIPER

5. 5  Optical interference filters  Longpass 650 nm for N 2 1P emission band  Bandpass 470/100 nm for N 2 + 1N emission band  50 mm f/1.4 Canon lenses  16 mm x 16 mm active photometer area  Produces 18 degree square field of view  Hamamatsu C4900 photometer power supply  15 V in to –1200 V out  64 8-pole Chebyshev anti-aliasing filters  Cutoff at 12 kHz to allow 25 kHz sampling  Two National Instruments PCI-6254 DAQ cards  Photodiode-controlled CS45 electronic shutters

6. Introduction to PIPER 6

7. 7 Imaging With PIPER Photometer Data =182 12 14 13 11 16 14 14 13 11 20 19 21 26 20 18 20 13 19 24 44 53 42 35 28 14 20 30 43 55 50 43 32 17 18 25 43 50 48 45 35 17 20 26 41 49 48 42 40 16 18 25 35 36 36 33 34 13 14 20 24 25 24 23 24 Field of View =281 =107 =155 =258 =287 =283 =233 =167 =113=143=262=310=282=253=226 Photometer Pair

8. 8 Imaging With PIPER Sprite Evolving in Sky t = t 0 What Photometers See Photometers What PIPER Records

9. 9 Imaging With PIPER t = t 0 + T s What Photometers See Sprite Evolving in Sky Photometers What PIPER Records

10. 10 Imaging With PIPER t = t 0 + 2T s What Photometers See Sprite Evolving in Sky Photometers What PIPER Records

11. 11 Imaging With PIPER t = t 0 + 3T s What Photometers See Sprite Evolving in Sky Photometers What PIPER Records

12. 12 Imaging With PIPER t = t 0 + 4T s What Photometers See Sprite Evolving in Sky Photometers What PIPER Records

13. 13 Imaging With PIPER t = t 0 + 5T s What Photometers See Sprite Evolving in Sky Photometers What PIPER Records

14. 14 Imaging With PIPER t = t 0 + 5T s Integrated Camera Image What PIPER Records Sprite Evolving in Sky

15. 15 Imaging With PIPER Horizontal Photometer Data Vertical Photometer Data Camera Image time PIPER’s unit data product:

16. Imaging With PIPER 16 16 ms sprite images Images reduced to 16x16 pixels L2 norm reconstruction L1 norm reconstruction

17. Imaging With PIPER 17

18. 18 Observation Campaign  June 26, 2007 to August 2, 2007  Yucca Ridge Field Station  Near Fort Collins, Colorado  Instrumentation  PIPER w/ intensified camera  Wide-field-of-view intensified camera  Hi-speed camera on Dobsonian telescope  Stanford AWESOME VLF antenna/receiver

19. 19 July 10, 2007 Thunderstorm  Tracked July 10, 2007 Midwest thunderstorm  05:30 UT to 07:00 UT  moved southeast from southern South Dakota into northern Nebraska  Between 05:50 UT and 06:55 UT:  20 sprites observed by wide field of view camera direction of storm sprites observed in this region

20. 20 TLE at 06:01:46 UT Frame 1: 552 ms to 569 ms PIPER field of view

21. 21 TLE at 06:01:46 UT Frame 2: 570 ms to 586 ms

22. 22 TLE at 06:01:46 UT Frame 3: 586 ms to 603 ms

23. 23 TLE at 06:01:46 UT Frame 4: 603 ms to 619 ms

24. 24 TLE at 06:01:46 UT Frame 5: 619 ms to 636 ms

25. 25 TLE at 06:01:46 UT Frame 6: 636 ms to 652 ms

26. 26 TLE at 06:01:46 UT Frame 7: 652 ms to 669 ms

27. 27 TLE at 06:01:46 UT Frame 8: 669 ms to 686 ms

28. 28 TLE at 06:01:46 UT Frame 9: 686 ms to 703 ms

29. 29 TLE at 06:01:46 UT Frame 10: 703 ms to 719 ms

30. 30 TLE at 06:01:46 UT 12345 678910

31. 31 TLE at 06:01:46 UT 12345 678910 2 2

32. 32 TLE at 06:01:46 UT 12345 678910 3 3

33. 33 TLE at 06:01:46 UT 12345 678910 4 4

34. 34 TLE at 06:01:46 UT  Several distinct regions/events  elve (sub-millisecond), followed by  halo (~1 ms), followed by  gap (~1 ms), followed by  sprite (~30 ms) elve halo cloud reflection sprite light on horizon sprite halo gap elve

35. 35 Elve at 06:01:46 UT  Elve exhibits downward and radially outward expansion  In rangeward direction (which, when project to field of view, looks like downward motion) – left panel  In azimuthal direction – right panel  Consistent with observations of Barrington-Leigh +88.8 kA elve halo cloudflash halo

36. Other Elves 36 (from Barrington-Leigh, 2001) +210.9 kA  Appeared as dim sprite in video  Appeared as bright elve+sprite in PIPER

37. 37 Other Elves  Appeared as dim sprite in video  Appeared as bright elve+sprite in PIPER +99.6 kA

38. Other Elves 38  Elve without sprite.  Not detected in video, only in PIPER.

39. Other Elves 39 -64.2 kA  Only one CG recorded by NLDN.  Nothing recorded on video.  Three (3) events recorded by PIPER.  Elve(s) appeared without sprite (-CG)

40. Other Elves 40 -66.9 kA -74.2 kA  Two more examples of possible multiple elves  (Vertical PIPER data only)  Not detected in video data; only in PIPER data

41. 41 Summary  PIPER is a photometric “camera”  recovers spatial resolution by using multi- anode photometers in pairs  In PIPER data, we see much that we don’t see in 60 field/sec video data  especially elves  and temporal development of sprites  Elves occur frequently  independently of sprites  sometimes in rapid succession