New perspectives on radiation belt precipitation from the ELFIN CubeSats

The Electron Losses and Fields Investigation (ELFIN) is a satellite mission
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launched in 2018 consisting of two, identical 3U CubeSats in circular, polar LEO orbit at altitudes ~450 km. Onboard each spacecraft, the ELFIN prime payloads consist of energetic particle telescopes and boom-deployed fluxgate magnetometers. Each orbit, ELFIN observes energetic electrons ranging from 50 keV to 7 MeV precipitating from Earth's radiation belts, and ELFIN presents the opportunity to study such radiation belt losses in unprecedented energy resolution with multipoint observations that enable some disambiguation of spatiotemporal evolution. Furthermore, the ELFIN spacecraft are spinners, revealing for the first time details of electron pitch angle distributions within the atmospheric loss cones. In this talk, we will introduce the ELFIN mission and system and payloads. Next, we present new results from ELFIN highlighting several enlightening features of outer radiation belt precipitation, including: energy spectra of> 1 MeV precipitation events and microbursts; spatial structure and temporal evolution of precipitation bands; evidence of localized regions of enhanced precipitation, presumably from chorus wave activity just outside the plasmapause; quantification of steady “drizzle” of electrons into the atmospheric loss cones vs. enhanced, time-limited microbursts and precipitation bands; and quantification of atmospheric backscatter of precipitating electrons. All of these are new insights enabled by the unique observations made possible from the multipoint ELFIN mission.