Title:

Quantifying Electron Precipitation from the Van Allen Radiation Belts

The spatial and temporal distribution of high energy electron precipitation from the Van Allen radiation belts is not well-understood. The FIREBIRD-II mission (2015-present) and the Van Allen Probes (2012-2019) provide a unique opportunity to examine the behaviors and drivers of high energy electron precipitation. This study quantifies electron precipitation as a function of radial distance (L-shell), local time (MLT), hemisphere, and geomagnetic indices (Kp). Electron precipitation was observed to peak at L-shell 4.5-5. Regions of elevated electron precipitation were identified at L-shell 4-6 at early late dawn (MLT 6-9) and dusk (MLT 15-21). Hemisphere filtering indicated very distinct regions of increased precipitation at late dawn and early dusk at L-shell 4-6 in the northern hemisphere, while the southern hemisphere showed overall more activity, as well as particularly increased activity at early dawn and late dusk. Precipitation at high Kp indices (Kp > 2) displayed elevated activity at all local times. In addition, multiple studies have proposed electromagnetic ion cyclotron (EMIC) waves as a potential driver of electron precipitation. This work searches for connections between EMIC waves observed by the Van Allen Probes and electron precipitation observed by FIREBIRD-II. During times of observed EMIC activity by the Van Allen Probes the FIREBIRD-II satellites recorded increased precipitation during MLT 0-3, MLT 6-9, and MLT 12-18, with activity being especially notable at MLT 15-18. This last region matches with a region of elevated EMIC wave occurrence rate observed in previous studies .

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