Coordinated Measurements of Transient Luminous Events
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Zev Levin, Yoav Yair, Colin Price, Peter Israelevich, Adam Devir, Baruch Ziv, Joachim Joseph, - PowerPoint PPT Presentation


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Coordinated Measurements of Transient Luminous Events - SPRITES – from the Space Shuttle and Ground Stations during MEIDEX. Zev Levin, Yoav Yair, Colin Price, Peter Israelevich, Adam Devir, Baruch Ziv, Joachim Joseph, Yuri Mekler, Meir Moalem. The Global Circuit 1. Ionosphere.

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Coordinated Measurements of Transient Luminous Events - SPRITES – from the Space Shuttle and Ground Stations during MEIDEX

Zev Levin,Yoav Yair, Colin Price,

Peter Israelevich, Adam Devir,

Baruch Ziv, Joachim Joseph,

Yuri Mekler, Meir Moalem


The Global Circuit 1

Ionosphere

Precipitation

Fair weather

field

Earth

250kV

  • The atmosphere is like a spherical capacitor with the outside charged positively and the inside (ground) charge negatively.

  • The potential difference between these two electrodes is about 250,000 Volts. Its average value remains fairly constant with time.


The global circuit 2
The Global Circuit 2

  • Although the atmosphere is a poor conductor an electrical current is continuously discharging the capacitor.

  • The electric field starts at about 120 V/M near the ground and decreases exponentially with height. At heights above clouds it is normally as low as 1 mV/m.

  • Lightning flashes are the generators that maintain the atmospheric electric field.


The charge distribution in thunderclouds
The Charge Distribution in Thunderclouds



Lightning
Lightning

  • Lightning are much more common over land than over the sea.

  • Most lightning strokes are inter cloud. They simply discharge the charge centers that have been developed.

  • About 40% of all flashes are cloud to ground and most of these are negative – bringing negative charge to ground.

  • About 10-20% of the flashes to ground are positive – positive charge to ground.

  • The reason for these positive flashes is not yet known, but its frequency of occurrence is related to either the tilt of the clouds and/or to the size of the storms (large mesoscale convective systems).


The ratio N = PGF/NGF varies during the lifetime

of the storm. Sometimes N > 1.

N=0.3

Early part of the storm


N=0.52

Mature part of the storm


N=6.25

Decaying part of the storm


Sprites
SPRITES

  • About 10 years ago, the Transient Luminous Emissions were first discovered and were given the names of Sprites (most common), Blue Jets and Elves.




Red sprites
Red Sprites

  • Usually associated with very strong PGFs (peak current > 130kA, 77% probability).

  • Stratiform region of MCS

  • Initiate at 70-75 km, moves both up and down.

  • Terminal height 85-90 km. Lifetime ~ few msec. 500 kR.

  • Speed: 107 m/sec.

  • Illuminated Volume > 104 km3.


Blue jets
Blue Jets

  • Not associated with PGFs, but occur in T-storms with intense NGF + hail + strong updrafts

  • Terminal altitude 32-43 km, Speed 112±24 km/sec. Ionized N2+

  • Not so rare, but hard to observe from the ground. 10 MR


Sprites from space
Sprites from Space

17 events from payload-Bay cameras during the MLE (Boeck et al, 1995)

STS 34 (1989), STS 32 (1990), STS 31 (1990), STS 41 (1990)STS 43 (1991), STS 48 (1991), STS 46 (1991)


Sprites observations with the meidex cameras
Sprites observations with the MEIDEX cameras

  • Primarily with the 665nm filter for Red Sprites and Elves and with the 380 and 470nm filters to record Blue Jets.

  • Continuous recording of the Earth’s limb from the direction of the dusk terminator towards the night side, preferably before midnight local time at the observed area.

  • The Astronaut will use the SEKAI LL-Video color camera to look for major thunderstorm centers.




Forecast of Measurements

Sprites --forecast of

regions of strong

convection and

cloud top temp. of around –70C


Meidex sprite rois
MEIDEX-Sprite ROIs Measurements



Ground observations israel
Ground Observations: Israel Measurements

  • During the 16-day flight, two field sites in the Negev Desert in Israel will be used to collect ELF (SR) and VLF data related to sprite activity.

  • Both are operated by TAU.


Global ground observations
Global Ground Observations Measurements

  • Optical measurements: Japan (Osaka, Sendai), Taiwan (Taipei), USA – YRFS, Stanford (?)

  • ELF measurements: Long Island, Hungary, Antarctica

  • VLF network: Germany, S.Africa, Chile, California, New-Zealand, Japan; USA (Duke)

  • Lightning Location Systems: Japan, Brazil, NLDN


Summary
Summary Measurements

  • Unique opportunity for global coverage

  • Multi-sensor measurements

  • The first ever spectral Calibrated measurements from space


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