Resolving Magnetopause Shadowing Using Multi-Mission Measurements of
Phase Space Density
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. Whilst
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, multi-spacecraft 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. 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 towards the magnetopause boundary.