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/

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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

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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-L1616-anode photometers 18 degree fields of view Operate in pairs Turned at right angles

Augmented w/ video camera(not shown)

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Introduction to PIPER

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Introduction to PIPER

Optical interference filters Longpass 650 nm for N2 1P emission band Bandpass 470/100 nm for N2

+ 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 Vin to –1200 Vout

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

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Imaging With PIPER

Photometer Data

=1

82

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=1

13

=1

43

=2

62

=3

10

=2

82

=2

53

=2

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Photometer Pair

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Imaging With PIPER

Sprite Evolving in Sky

t = t0

What Photometers See

Photometers

What PIPER Records

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Imaging With PIPER

t = t0 + Ts

What Photometers See

Sprite Evolving in Sky Photometers

What PIPER Records

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Imaging With PIPER

t = t0 + 2Ts

What Photometers See

Sprite Evolving in Sky Photometers

What PIPER Records

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Imaging With PIPER

t = t0 + 3Ts

What Photometers See

Sprite Evolving in Sky Photometers

What PIPER Records

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Imaging With PIPER

t = t0 + 4Ts

What Photometers See

Sprite Evolving in Sky Photometers

What PIPER Records

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Imaging With PIPER

t = t0 + 5Ts

What Photometers See

Sprite Evolving in Sky Photometers

What PIPER Records

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Imaging With PIPER

t = t0 + 5Ts

Integrated Camera Image

What PIPER Records

Sprite Evolving in Sky

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Imaging With PIPER

HorizontalPhotometer

Data

VerticalPhotometer

Data

CameraImage

time

time

PIPER’s unitdata product:

Imaging With PIPER

16

16 m

s sp

rite

imag

es

Imag

es r

educ

ed to

16x

16 p

ixel

s

L2

norm

rec

onst

ruct

ion

L1

nor

m r

econ

stru

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Imaging With PIPER

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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

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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 observedin this region

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TLE at 06:01:46 UT

Frame 1: 552 ms to 569 ms

PIPER field of view

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TLE at 06:01:46 UT

Frame 2: 570 ms to 586 ms

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TLE at 06:01:46 UT

Frame 3: 586 ms to 603 ms

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TLE at 06:01:46 UT

Frame 4: 603 ms to 619 ms

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TLE at 06:01:46 UT

Frame 5: 619 ms to 636 ms

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TLE at 06:01:46 UT

Frame 6: 636 ms to 652 ms

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TLE at 06:01:46 UT

Frame 7: 652 ms to 669 ms

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TLE at 06:01:46 UT

Frame 8: 669 ms to 686 ms

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TLE at 06:01:46 UT

Frame 9: 686 ms to 703 ms

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TLE at 06:01:46 UT

Frame 10: 703 ms to 719 ms

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TLE at 06:01:46 UT

1 2 3 4 5

6 7 8 9 10

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TLE at 06:01:46 UT

1 2 3 4 5

6 7 8 9 10

2

2

32

TLE at 06:01:46 UT

1 2 3 4 5

6 7 8 9 10

3

3

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TLE at 06:01:46 UT

1 2 3 4 5

6 7 8 9 10

4

4

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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)

elveelvehalo

cloud reflection

sprite

light on horizonlight on horizon

sprite

halo

gap

gap

elve

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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

elve

halo

cloudflash

halo

Other Elves

36(from Barrington-Leigh, 2001)

+210.9 kA

Appeared as dim sprite in video

Appeared as bright elve+sprite in PIPER

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Other Elves

Appeared as dim sprite in video

Appeared as bright elve+sprite in PIPER

+99.6 kA

Other Elves

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Elve without sprite. Not detected in video, only in PIPER.

Other Elves

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-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)

Other Elves

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-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

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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