Electron acceleration in the near-Earth magnetotail: test particle calculations in electromagnetic fields from two-dimensional hybrid simulations

Abstract

Electron acceleration in the near-Earth magnetotail during the substorm period is still an unresolved question. In this paper, by tracing electron trajectories in the dynamically evolving electromagnetic fields obtained from a two-dimensional (2D) global hybrid simulation, we investigate electron acceleration in the near-Earth magnetotail during dipolarization. In our simulation, electrons with energies above several keV can gain energy in the plasma sheet due to the adiabatic acceleration mechanism when these electrons propagate earthward. In the near-Earth magnetotail (about 9–15 $R_{E}$ from the Earth), these electrons can be accelerated by betatron acceleration which is due to the compression of magnetic field associated with dipolarization of magnetotail. Additionally, in the middle and high latitudes of the near-Earth magnetotail, the parallel electric field carrying by kinetic Alfven waves can also accelerate electrons when these electrons bounce between the mirror points. The combination effects of these three acceleration mechanisms can accelerate electrons from several keV to about one hundred keV. Our results indicate that both the large-scale structure and wave-particle interactions need to be taken into account for electron acceleration in the near-Earth magnetotail.