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

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 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 Introduction to PIPER

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

Introduction to PIPER 6

7 Imaging With PIPER Photometer Data = Field of View =281 =107 =155 =258 =287 =283 =233 =167 =113=143=262=310=282=253=226 Photometer Pair

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

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

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

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

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

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

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

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

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

Imaging With PIPER 17

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

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

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

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

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

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

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

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

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

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

30 TLE at 06:01:46 UT

31 TLE at 06:01:46 UT

32 TLE at 06:01:46 UT

33 TLE at 06:01:46 UT

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 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 kA elve halo cloudflash halo

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

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

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

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

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

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