Electron energization in the geomagnetic tail current sheet

Abstract

Electron motion in the distant tail current sheet is evaluated and found to violate the guiding center approximation at energies ≳ 100 eV. Most electrons within the energy range ˜10−1 ‐ 10² keV that enter the current sheet become trapped within the magnetic field reversal region. These electrons then convect earthward and gain energy from the cross‐tail electric field. If the energy spectrum of electrons entering the current sheet is similar to that of electrons from the boundary layer surrounding the magneto tail, the energy gain from the electric field produces electron energy spectra comparable to those observed in the earth's plasma sheet. Thus current sheet interactions can be a significant source of particles and energy for plasma sheet electrons as well as for plasma sheet ions. A small fraction of electrons within the current sheet has its pitch angles scattered so as to be ejected from the current sheet within the atmospheric loss cone. These electrons can account for the electron precipitation near the high‐latitude boundary of energetic electrons, which is approximately isotropic in pitch angle up to at least several hundred keV. Current sheet interaction should cause approximately isotropic auroral precipitation up to several hundred keV energies, which extends to significantly lower latitudes for ions than for electrons in agreement with low‐altitude satellite observations. Electron precipitation associated with diffuse aurora generally has a transition at 1–10 keV to anisotropic pitch angle distributions. Such electron precipitation cannot be explained by current sheet interactions, but it can be explained by pitch angle diffusion driven by plasma turbulence.