correlated high speed video, medium range e...
TRANSCRIPT
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1
Correlated High Speed Video, Medium Range E-Field, and B-field observations of Sprites
Takeshi Kammae, H.C. Stenbaek-Nielsen
Geophysical Institute, University of Alaska
Matthew G. McHargSpace Physics & Atmospheric
Research Center and Physics Dept., US Air Force Academy
AE14A-02 (16:15)
Steven A. Cummer, Gaopeng Lu, & Jingbo Li
Electrical and Computer Engineering Department, Duke University
William W. HagerDepartment of Mathematics,
University of Florida
R. K. HaalandPhysics and Engineering Dept.
Ft. Lewis College
Richard SonnenfeldDepartment of Physics and Langmuir
Laboratory, New Mexico Tech
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2(Some) Prior Work• Sprites associated with large +CG flashes
(Boccippio et al., Science 1995)
• Brightness proportional to current, driven by field (Pasko, et al., JGR 1997)
• Sprites delayed up to 120 ms from parent flash(Li, Cummer, et al., JGR 2008)
• VLF (B-field) measurements see effect from sprite itself in ~10% of cases(Cummer, Inan et al., GRL 1998)
AE14A-02
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3Goals
Measure time between lightning flash and sprite initiation.
Correlate E-field and B-field.
Look for current signature of sprite in Electric field records.
Look for electrostatic signature of sprite.
AE14A-02
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4Langmuir Electric field Array
Network of eight field-change stations
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5Langmuir Electric field Array
GPS disciplined timing
Digitize with three different sensitivities.
Sample period is 20 microsec.
10 mV/m < E < 400 kV/m
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67/15/10 7:06:09.808 UTSprite “A”
Closest ...
DLANGMUIR=275 km
DDUKE= 2600 km
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7Sprite “A”
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8Time Delaysfrom first Field change to first light
Parent Flash Information7/13/10 6:03:04.263 29.36 -109.65 221.0 kA
7/15/10 5:22:01.710 34.34 -102.21 68.0 kA B 5:27:09.694 34.24 -102.10 80.0 kA 5:32:57.564 34.36 -102.31 33.0 kA 5:45:14.489 34.16 -102.16 8.0 kA 5:55:54.807 34.38 -102.08 51.0 kA 6:41:36.081 34.02 -103.40 78.0 kA 7:00:31.844 34.00 -103.32 53.0 kAA 7:06:09.808 33.80 -103.93 111.0 kA
Time Delay (ms)
< 0.5
5.3 1.5 1.8 5.0
3.3 1.5 1.5 0.5
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9
No evidence of sprite in E-field
Sprite “A”
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10
No evidence of sprite in E-field
Sprite “A”
Model suggests I < 3 kA
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117/15/10 5:27:09.695 UT
IPEAK=30 kA
v=107 m /s
Q=45C
M=650C⋅km
Sprite “B”
D=470 km
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12Sprite “B”: Clear sprite signature in E
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13Sprite “B”: E-field signature
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14Sprite “B”: E-field signatureWaveform highly reproducible. Thus not a nearby flash (or a cow).
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15Sprite “B”: EM signature
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16
B and E both show sprite effect
Sprite “B”: EM signature
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17
B = E/cdistance dependence
~1/r
Return stroke in B has ionospheric bounce
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18
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19
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20Conclusions
Clear sprite E-field signature in 1 of 9 sprite flashes.
E-field and B-field signatures similar.
E-field effects look proportional to current.
No electrostatic effects observed.
All sprites were “prompt” (delays < 5 millisec).
Distance dependence of E and B is 1/r.
B = E/c as expected.
AE14A-02
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21Event “A”
Propagation time consistent w/ location
to 150 km.
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22Instrumentation
Description
Telescopic video (Phantom7)
Langmuir Electric Field-change array
Duke VLF facility
National Lightning Detection Network
Time Resolution
80
20
10
1000
s
s
s
s