Differentiating Between Simultaneous Loss Drivers in Earth's Outer Radiation Belt: Multi‐Dimensional Phase Space Density Analysis

F. A. Staples*, Qianli Ma, Adam Kellerman, I. J. Rae, Colin Forsyth, J. K. Sandhu, Jacob Bortnik

*Corresponding author for this work

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Abstract

We analyzed the contribution of electromagnetic ion cyclotron (EMIC) wave driven electron loss to a flux dropout event in September 2017. The evolution of electron phase space density (PSD) through the dropout showed the formation of a radially peaked PSD profile as electrons were lost at high L*, resembling distributions created by magnetopause shadowing. By comparing 2D Fokker Planck simulations of pitch angle diffusion to the observed change in PSD, we found that the μ and K of electron loss aligned with maximum scattering rates at dropout onset. We conclude that, during this dropout event, EMIC waves produced substantial electron loss. Because pitch angle diffusion occurred on closed drift paths near the last closed drift shell, no radial PSD minimum was observed. Therefore, the radial PSD gradients resembled solely magnetopause shadowing loss, even though the local pitch angle scattering produced electron losses of several orders of magnitude of the PSD.
Original languageEnglish
Article numbere2023GL106162
Number of pages11
JournalGeophysical Research Letters
Volume50
Issue number23
Early online date7 Dec 2023
DOIs
Publication statusPublished - 16 Dec 2023

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