Abstract
Loss mechanisms act independently or in unison to drive rapid loss of electrons in the radiation belts. Electrons may be lost by precipitation into the Earth's atmosphere, or through the magnetopause into interplanetary space—a process known as magnetopause shadowing. While magnetopause shadowing is known to produce dropouts in electron flux, it is unclear if shadowing continues to remove particles in tandem with electron acceleration processes, limiting the overall flux increase. We investigated the contribution of shadowing to overall radiation belt fluxes throughout a geomagnetic storm starting on the 7 September 2017. We use new, multimission phase space density calculations to decipher electron dynamics during each storm phase and identify features of magnetopause shadowing during both the net‐loss and the net‐acceleration storm phases on sub‐hour time scales. We also highlight two distinct types of shadowing; “direct,” where electrons are lost as their orbit intersects the magnetopause, and “indirect,” where electrons are lost through ULF wave driven radial transport toward the magnetopause boundary.
Highlights
The outer radiation belt is a ring of relativistic electrons which are trapped by Earth's magnetosphere, surrounding the Earth at distances from ∼3 to 8 Earth Radii above Earth's surface
We presented an overview of the outer electron radiation belt response to a sequence of interacting coronal mass ejecta (CME) and interplanetary shocks propagating through the solar wind in early September 2017
As the solar wind characteristics of this event have already been studied in detail (e.g., Scolini et al, 2020; Shen et al, 2018; Werner et al, 2019), we do not analyze these in detail, instead we focus on the relativistic electron response to these drivers
Summary
Multimission phase space density observations are necessary to resolve relativistic electron dynamics during September 2017 storm. Relativistic electron losses to the magnetopause were identified, which led to further diffusion of electrons toward the magnetopause. Electron loss to the magnetopause was observed simultaneous to prompt local energization in the heart of the radiation belt. Supporting Information: Supporting Information may be found in the online version of this article. Resolving Magnetopause Shadowing Using Multimission Measurements of Phase Space Density.
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