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On remote sensing of TLEs On remote sensing of TLEs by ELF/VLF wave by ELF/VLF wave

measurements on board a measurements on board a satellitesatellite

F. LefeuvreF. Lefeuvre11, R. Marshall, R. Marshall22, J.L. Pinçon, J.L. Pinçon11, U.S. , U.S. InanInan22, D. Lagoutte, D. Lagoutte11, M. Parrot, M. Parrot11, J.J. , J.J. BerthelierBerthelier33

11 LPCE/CNRS, 3 A, Av de la Recherche scientifique, 45071, LPCE/CNRS, 3 A, Av de la Recherche scientifique, 45071, Orléans cedex 2, France, Orléans cedex 2, France, lefeuvrelefeuvre@@cnrs-orleans.frcnrs-orleans.fr22 STARLAB, Stanford Univ., Stanford CA 94305-9515, USA STARLAB, Stanford Univ., Stanford CA 94305-9515, USA33 CETP, 4, av de Neptune, 94107 Saint Maur des Fossés, CETP, 4, av de Neptune, 94107 Saint Maur des Fossés, FranceFrance

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ContextContext

Ground-based EM observations in Ground-based EM observations in the ELF/VLF band allow the the ELF/VLF band allow the detection of:detection of:- parent lightning - parent lightning - currents in the heart of sprites- currents in the heart of sprites- ELF slow-tails, etc.- ELF slow-tails, etc.

Space-based EM observationsSpace-based EM observations- space based characterization of parent - space based characterization of parent lightning in the VHF band (FORTE)lightning in the VHF band (FORTE)

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The present paper based on The present paper based on simultaneous observations:simultaneous observations:

- at ground: Stanford Langmuir (and - at ground: Stanford Langmuir (and Palmer ) stationsPalmer ) stations

- on the French DEMETER satellite- on the French DEMETER satellite

is a first attempt to try to point out information is a first attempt to try to point out information we can get from EM measurements:we can get from EM measurements:

- in the ELF/VLF frequency range- in the ELF/VLF frequency range- with an extension on higher frequency - with an extension on higher frequency bandsbands

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Central question:Central question:

How does EM waves radiated by How does EM waves radiated by lightning flashes cross the ionosphere ?lightning flashes cross the ionosphere ?

According to the « sharp-boundary » model ?

According to a« radio-window » model ?

B0 B0

Pk

sferics

0+ whistlers

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PLANPLAN

1. Introduction1. Introduction2. Instrumentation2. Instrumentation3. data and interpretation of 3. data and interpretation of resultsresults4. discussion4. discussion5. conclusion5. conclusion

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2. INSTRUMENTATION2. INSTRUMENTATION

Ground-based measurements Ground-based measurements

● ● Langmuir station (33° 9 N, 252°8 E)Langmuir station (33° 9 N, 252°8 E)

- low-light camera system, photometer data at 25 - low-light camera system, photometer data at 25 kS/skS/s- ELF/VLF measurements (~350 Hz to 45 kHz)- ELF/VLF measurements (~350 Hz to 45 kHz)

The locations of causative lightning strokes were The locations of causative lightning strokes were determined to an accuracy of ± 0.5 km by the US determined to an accuracy of ± 0.5 km by the US National Lightning Detection NetworkNational Lightning Detection Network

● ● Palmer station, Antarctica (64°77 S, 296° Palmer station, Antarctica (64°77 S, 296° E)E)

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DEMETER measurementsDEMETER measurements

● Orbit● Orbit

- circular Sun-synchronous polar orbit at an altitude - circular Sun-synchronous polar orbit at an altitude of 710 kmof 710 km - night time passes over Langmuir around 22:30 - night time passes over Langmuir around 22:30 MLT. MLT.

● TBF experiment● TBF experiment

- ELF band (≤ 1 kHz), 2 electric and 3 magnetic wave - ELF band (≤ 1 kHz), 2 electric and 3 magnetic wave field components field components - VLF band (≤ 17 kHz), 1 electric at 1 magnetic wave - VLF band (≤ 17 kHz), 1 electric at 1 magnetic wave field componentsfield components

- burst modes (waveform data) over predefined - burst modes (waveform data) over predefined geographical zonesgeographical zones

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L

Juillet 28 2005 DEMETER orbit above the New Mexican Langmuir station (L)

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Sf1 Sf2 Sf3 GROUND-BASED

Two TLEs are observed- TLE1, 05:02:44.678 UT- TLE2, 05:02:44.751 UT

Thee sferic events- Sf1 (7ms before TLE1, at the time of a lightning (CG+, 75.2 kA)- Sf2 (41 ms before TLE2, at the time of a lighting (CG+ , 28 kA)- Sf3 (cluster of sferics starting 10 ms before TLE2

Palmer data- 34 ms after Langmuir- amplitude 10 time less

Waveforms- Langmuir, EM signature of ELF- Palmer, slow tail

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0+2 0+30+1

0+1 0+30+2

DEMETER

Three EM (E and B spectra )0+ whistlers associatedwith the three sferics observedat Langmuir

Power : 65 dB less than atLangmuir

However, distance betweenthe DEMETER magneticFoot line and Langmuir ~ 880 km

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248° 252° 256° 258° E

36°

32°

28°

24°

Geographical location of: the lightning area ( ), the Langmuirstation ( ), the DEMETER magnetic foot line ( )

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Note :Note :

Langmuir spectrogramLangmuir spectrogramthe lack of substantial attenuation < 1.8 kHz the lack of substantial attenuation < 1.8 kHz

could mean that the could mean that the wave propagates directly wave propagates directly upwardupward

Palmer spectrogramPalmer spectrogramthe lower frequency cut-off at ~ 1.6 kHz the lower frequency cut-off at ~ 1.6 kHz

suggests that the wave suggests that the wave does not propagate in the does not propagate in the wave guide QTEM modewave guide QTEM mode

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16 - 20 kHz~ 1ms

Pulse like feature before 0+ whistler 1 (as Kelley et al. 1990), but Kelley et al. (1997) show maximum power of lightning EM in the 50 – 125 kHz) frequency range

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Proton whistlers-upgoing by definition- R part (electron whistler)- L part (proton whistler)

Observation :- R and L waves seen on E and B spectra- no energy gap on the R wave between fcr and fH

+

Agreement with theWang (1971) model :-the « electron whistler » propagates with θ~0° ,-the « proton whistler » propagates with large θ values-The DEMETER observation explained for 0 < θ < 30°.

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3. Discussion3. Discussion

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RADIO – WINDOW THEORY (Ellis, 1956; RADIO – WINDOW THEORY (Ellis, 1956; Budden, 1985)Budden, 1985)

nn22 = 1 – A/ ( B± C) = 1 – A/ ( B± C)

A = X(U-X)A = X(U-X)B = U(U-X) - 0.5YB = U(U-X) - 0.5YTT

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C ={ 0.25 YC ={ 0.25 YTT44 + + YYLL

2 2 (U-X)}(U-X)}1/21/2

X = fX = fpepe22/f/f22

Y = fY = fcece/f/fθ = (Bθ = (B00, K), K)YYT T = Y sin θ = Y sin θ YYL L = Y cos θ = Y cos θ

U = 1 – iZU = 1 – iZZ = ν/2πf, with ν electron collision frequencyZ = ν/2πf, with ν electron collision frequency

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Variation of n2 as a function of X = fpe2/f2 for a cold collisionless

electron plasma at Y = fce/f = 100.

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IRI 2001 model of ionosphere for July 28 2005 at the UT time and at thegeographical coordinates of the observations at Langmuir and DEMETER.Collision frequency model ν= K exp {-0.15(h-h0)}

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300 kHz

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CONCLUSIONCONCLUSION

The analysis of the 28 July 2005 The analysis of the 28 July 2005 eventsevents, simultaneously observed at the , simultaneously observed at the Langmuir station and on-board Langmuir station and on-board DEMETER, at the time of TLEs detection, DEMETER, at the time of TLEs detection, show that: show that:

- parent lightning flashes may be - parent lightning flashes may be identified from satellite measurements in identified from satellite measurements in the ELF/VLF band,the ELF/VLF band,

- proton whistlers characteristics may be - proton whistlers characteristics may be used for fast estimation of propagation used for fast estimation of propagation characteristics after ionospheric crossingcharacteristics after ionospheric crossing

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The Ellis, Budden « radio window » conceptThe Ellis, Budden « radio window » concept

- explains the July 28 2005 observation- explains the July 28 2005 observation

- suggests that its effects are quite general- suggests that its effects are quite general

To better understand the effects of the To better understand the effects of the ionospheric crossingionospheric crossing, one needs , one needs

- better models of the D and E layers- better models of the D and E layers

- ray-tracing programs taking into account collisions, - ray-tracing programs taking into account collisions, heavy ions, etc.heavy ions, etc.

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NOTE :NOTE :

The theory predicts that the condition for a wave The theory predicts that the condition for a wave energy transmission depends on the latitude of the energy transmission depends on the latitude of the transmission point, and so that is only possible for Y > transmission point, and so that is only possible for Y > 0.5 (1+l0.5 (1+lzz

-2-2), with lz the direction cosine of the axis of ), with lz the direction cosine of the axis of the refractive index surface.the refractive index surface.

As a consequence waves which may be transmitted As a consequence waves which may be transmitted must have angles between B0 and the vertical must have angles between B0 and the vertical - < 85° at 1 kHz, - < 85° at 1 kHz, - < 80° at 5 kHz, etc - < 80° at 5 kHz, etc

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From J.L. Pinçon