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Combined Optical and Radio-Frequency Measurements of a Lightning Megaflash by the FORTE Satellite
  • Michael Jay Peterson,
  • Tracy Ellen Lavezzi Light,
  • Xuan-Min Shao
Michael Jay Peterson
ISR-2,Los Alamos National Laboratory

Corresponding Author:michaeljp24@gmail.com

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Tracy Ellen Lavezzi Light
Los Alamos National Laboratory (DOE)
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Xuan-Min Shao
Los Alamos National Laboratory (DOE)
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The optical and VHF instrumentation on the FORTE satellite is used to document the combined phenomenology evolution of a lightning “megaflash” - mesoscale lightning that propagates laterally over exceptional distances. We identify a FORTE flash whose maximum extent was 82 km and inferred length over multiple distinct branches exceeded 100 km. This flash lasted 1.2 s and produced 250 optical and 591 RF events. We find that the channel development mapped by FORTE’s pixelated lightning imager (LLS) occurred at a typical speed of 2.6x10^5 m/s and was accompanied by sustained periods VHF emission that could individually exceed 100 ms in duration. The impulsive IC events generated by the flash indicate that this development occurred at altitudes between 3 and 8 km. Four +CG strokes were identified in the VHF waveform data that are responsible for two of the three highly-radiant LLS groups (the third radiant group came from a possible -CG while 2 of the +CGs were not as optically bright as the others). These strokes occurred at different locations throughout the flash footprint with the most distant strokes separated by approximately 50 km. These space-based observations match previous observations of megaflashes from space as well as ground-based measurements of slow negative leader development during “spider” lightning, suggesting that FORTE is sensing the same phenomena.
16 Aug 2021Published in Journal of Geophysical Research: Atmospheres volume 126 issue 15. 10.1029/2020JD034411