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Abstract

A distinct population of ultrarelativistic electrons has been observed in the outer radiation belt after several geomagnetic storms, and recent modeling results indicate that an existing seed population, and depletions in plasmasphere electron density, are a necessary condition for the appearance of this electron population. In order to similarly deepen our understanding of the solar wind drivers behind the appearance of these electrons with extreme energy, we catalog storms corresponding to ultrarelativistic enhancements by origin, and begin to establish necessary and sufficient solar wind conditions for these enhancement events. To do so, we perform superposed epoch analysis on a 6 year period from 2012 to 2018, using solar wind data from the Omniweb service, as well as electron flux and electron density data products from the Van Allen Probes mission. We also consider connections to wave-particle interactions by including a chorus wave proxy in the analysis, and provide an overview of further modeling objectives and open questions for continued investigation of this electron population.