Lightning-Induced Electron Precipitation Events Observed at Low Altitudes

Abstract

Lightning-induced electron precipitation (LEP) events are important phenomena in the Earth's inner magnetosphere, where atmospheric lightning strokes cause energetic electron loss from the radiation belts. Lightning strokes generate electromagnetic waves that penetrate the ionosphere and propagate through the Earth's magnetosphere as so-called lightning-generated whistlers. They interact with radiation belt electrons, decreasing their pitch angles and causing their eventual loss in the atmosphere. At low altitudes, LEP events in satellite data are characterized by a sudden increase in wave intensity across a wide range of frequencies accompanied by an increase in precipitating electron flux. We detect and analyze LEP events using wave and particle burst mode data measured by the DEMETER satellite between 2004 and 2010. We develop a semi-automatic procedure to identify these events, detecting more than 400 events in total. The identified events mostly occur at L-shells between approximately 2 and 3.75, and extend up to energies of about 200 keV. Most events are detected above the U.S. East Coast, possibly related to significant lightning activity and the location westward of the South Atlantic Anomaly. Finally, we estimate total precipitating electron fluxes and wave intensities based on the average LEP properties and lightning occurrence rate, and we show that the individual isolated LEP events appear to be insufficient to explain the observed summer-winter differences in the precipitating electron fluxes above the U.S. region.