Depletions of multi-MeV Electrons and Their Association to Minima in
Phase Space Density
Abstract
Fast-localized electron loss, resulting from interactions with
electromagnetic ion cyclotron (EMIC) waves, can produce deepening minima
in phase space density (PSD) radial profiles. Here, we perform a
statistical analysis of local PSD minima to quantify how readily these
are associated with radiation belt depletions. The statistics of PSD
minima observed over a year are compared to the Versatile Electron
Radiation Belts (VERB) simulations, both including and excluding EMIC
waves. The observed minima distribution can only be achieved in the
simulation including EMIC waves, indicating their importance in the
dynamics of the radiation belts. By analyzing electron flux depletions
in conjunction with the observed PSD minima, we show that, in the heart
of the outer radiation belt (L*<5), up to 45% of multi-MeV
electron depletions are associated with PSD minima, demonstrating that
fast localized loss by interactions with EMIC waves are a common and
crucial process for ultra-relativistic electron populations.