Upper Limit of Electron Energization in the Near-Earth Plasma Sheet during Substorm Injections

Abstract: The Earth's magnetotail, located on the night side of the magnetosphere, is a dynamic region where magnetic field energy is released and converted into plasma heating, particle acceleration, and kinetic energy through magnetic reconnection. Recent low-altitude observations from the CIRBE CubeSat reveal that the efficiency of particle acceleration in the magnetotail can be high enough to produce relativistic and ultra-relativistic electrons with energies reaching several MeV. To investigate the underlying acceleration mechanisms, we used the Rice Convection Model (RCM) to simulate the observed magnetotail electron populations. The simulations successfully reproduced key features of CIRBE observations, including the spectral shape and energy range of accelerated electrons. This agreement between RCM results and CIRBE observations offers crucial insights into the physical processes responsible for extreme electron acceleration events in the magnetotail.