Transient Luminous Events (TLEs)
and Early VLF events
Prepared by Robert Marshall, Benjamin Cotts, and Morris Cohen
Stanford University, Stanford, CA
IHY Workshop on
Advancing VLF through the Global AWESOME Network
The Most Famous TLEs: Sprites
2
Transient Luminous Events
3
Sprites
4
Sprite Observing Equipment
High-speed cameras
Cummer et al [2006].
5
Sprite Movie
from Stenbaek-Nielsen, H. C., et al, (2007), GRL, 34, L11105
6
Sprites and the Quasi-Electrostatic
Field
•
Transient: endure <50 ms, usually 1–2 ms
•
Luminous: intense red emissions (>1 GR)
•
Observed by low-light CCD video cameras
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Sprites and the Quasi-Electrostatic
Field
•
Transient: endure <50 ms, usually 1–2 ms
•
Luminous: intense red emissions (>1 GR)
•
Observed by low-light CCD video cameras
8
Sprites and the Quasi-Electrostatic
Field
•
Transient: endure <50 ms, usually 1–2 ms
•
Luminous: intense red emissions (>1 GR)
•
Observed by low-light CCD video cameras
•
Signature of quasi-electrostatic field
9
Sprites and the Quasi-Electrostatic
Field
•
Transient: endure <50 ms, usually 1–2 ms
•
Luminous: intense red emissions (>1 GR)
•
Observed by low-light CCD video cameras
•
Signature of quasi-electrostatic field
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Total Charge Moment
-
+ ++ + + +
+ ++ ++ +
+
+ +
-
+
-
 Total ELF energy is
proportional to total
charge transfer
 ELF energy attenuates
more in Earth-ionosphere
waveguide
Total charge moment
(I.e., C•km)
+ +
ELF Energy
Reising [1999]
Sprite-producing sferics
 Sprite producing
sferics have strong
ELF content
 Evidence of long
continuing currents
in lightning
 Nearly always has
positive polarity
Reising [1996]
ELF and sprite intensities
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Elves
•
First observed in 1992 (Space
shuttle)
•
Observed from ground by
cameras and photometers after
1996
Space Shuttle 2003 Yoav Yair [2003]
Elve
~90 km
Cloud Top (~20 km)
Modeling Optical Emissions
Marshall [2009]
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Elves and the Lightning-EMP
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Elve Movie: Expanding EMP
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Peak Current
+ ++ + + +
+ + + ++
+
+ + +
+
+
+
- - - - - - - - -
 Peak current is
proportional to VLF peak
 Higher peak current 
stronger EMP
Return stroke
peak current
(i.e., kA)
+ ++ + + +
+ +
VLF
Peak
Elve-producing sferics
Barrington-Leigh and Inan [1999]
 Elve-producing sferics have strong VLF content
 Evidence of high peak current, strong EMP
 Can result from either ‘+’ or ‘–’ polarity
The Gigantic Jet
Pasko et al. [2002]
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The Gigantic Jet
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From Pasko et al [2002]
TLEs Observed from Space: ISUAL
Sprites: 633, Gigantic Jets: 13
Elves: 5,434
Sprite halos: 657
21
From Chen et al, [2008]
Introduction to Early VLF Events
22
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Early VLF Event Properties
 Rapid onset delay (Dt < 20 ms)
 Rapid onset duration
(td < 20 ms)
 Typically recover in ~30-200 s
 Event amplitudes ~0.2-0.8 dB,
rarely >1 dB
 Forward scattering (< 30o)
 Causative CGs <50 km from
perturbed path
 Lateral extent of disturbances
~100 km
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Source: [Johnson and Inan 2000]
Early/fast Events in Broadband Data
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Sprites and Early VLF
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Early/fast Causative Mechanism
Theories
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Recent Results in TLE Observations
•
Observations from Space aboard ROCSAT-2, and upcoming TARANIS
– Chern et al [2003], Mende et al [2005], Frey et al [2005]
– Lefeuvre et al [2006] (AGU Fall Meeting), Blanc et al [2007] (Adv. Space Res.)
•
Correlations between sprites, early/fast, and sferic bursts
– Ohkubo et al [2005], Van der Velde et al [2006], Marshall et al [2006,2007]
•
Sprites observed at 5,000 frames per second and higher
– Cummer et al [2006], Nielsen et al [2007], McHarg et al [2007]
•
3D Modeling of elves
– Marshall et al [2008]
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Questions for Future TLE Research
•
Where else do sprites occur? Over what types of storms? To date,
mostly over Mesoscale Convective Systems
– Inexpensive ground-based cameras and photometers
•
How many elves occur compared to sprites? Over what storms?
– Ground-based photometers and sensitive, triggered cameras
•
How many sprites have correlated early/fast events? What is the
polarity of these events? What are the lightning signatures?
– VLF receivers near sprite locations, preferably also near Lightning detection
networks / VHF receiver networks
•
What types of storms produce Jets? Is Lightning correlated? Is there a
VLF signature of Jets?
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