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

c - 2 The Global Circuit 1 Precipitation Earth Fair weather field Ionosphere 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.

c - 3 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.

c - 4 The Charge Distribution in Thunderclouds

c - 5 Global Lightning Distribution for June 1999

c - 6 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).

c - 7 N=0.3 The ratio N = PGF/NGF varies during the lifetime of the storm. Sometimes N > 1. Early part of the storm

c - 8 N=0.52 Mature part of the storm

c - 9 N=6.25 Decaying part of the storm

c - 10 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.

c - 11 Sprites etc.

c - 12 Transient Luminous Events

c - 13 Red Sprites zUsually associated with very strong PGFs (peak current > 130kA, 77% probability). zStratiform region of MCS zInitiate at km, moves both up and down. zTerminal height km. Lifetime ~ few msec. 500 kR. zSpeed: 10 7 m/sec. zIlluminated Volume > 10 4 km 3.

c - 14 Blue Jets zNot associated with PGFs, but occur in T- storms with intense NGF + hail + strong updrafts zTerminal altitude km, Speed 112±24 km/sec. Ionized N 2 + zNot so rare, but hard to observe from the ground. 10 MR

c - 15 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)

c - 16 Sprites observations with the MEIDEX cameras zPrimarily with the 665nm filter for Red Sprites and Elves and with the 380 and 470nm filters to record Blue Jets. zContinuous 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. zThe Astronaut will use the SEKAI LL-Video color camera to look for major thunderstorm centers.

c - 17 On-Orbit Operations and Ground Stations for Sprite Measurements Chile

c - 18 Configuration for Viewing Sprites

c - 19 Forecast of Sprites -- forecast of regions of strong convection and cloud top temp. of around –70C

c - 20 MEIDEX-Sprite ROIs

c - 21 The atmosphere as a wave guide

c - 22 Ground Observations: Israel zDuring 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. zBoth are operated by TAU.

c - 23 Global Ground Observations zOptical measurements: Japan (Osaka, Sendai), Taiwan (Taipei), USA – YRFS, Stanford (?) zELF measurements: Long Island, Hungary, Antarctica zVLF network: Germany, S.Africa, Chile, California, New-Zealand, Japan; USA (Duke) zLightning Location Systems: Japan, Brazil, NLDN

c - 24 Summary zUnique opportunity for global coverage zMulti-sensor measurements zThe first ever spectral Calibrated measurements from space