High-speed electron flows in the terrestrial magnetotail

Abstract

High-speed electron flows play a crucial role in the energy dissipation and conversion processes within the terrestrial magnetosphere, particularly in regions associated with magnetic reconnection, such as the vicinity of electron diffusion regions (EDRs) and separatrix layers. NASA's Magnetospheric Multiscale (MMS) mission was specifically designed to reveal electron-scale kinetic processes occurring in Earth's magnetosphere. In this study, we conduct a comprehensive survey of high-speed electron flows in the terrestrial magnetotail, utilizing MMS observations spanning from 2017 to 2021. Our analysis identifies a total of 642 events characterized by electron bulk speeds exceeding 5,000 km/s. Notably, these events exhibit a clear dawn-dusk asymmetry, with 73% of them occurring in the dusk magnetotail. Along the magnetotail's normal direction, we find that 37.7%, 21.8%, and 40.5% of the events are located in the plasma sheet, plasma sheet boundary layer, and lobe region, respectively. The occurrence rate of these events peaks when the magnetic field strength is approximately 19 nT. High-speed electrons predominantly move along magnetic field lines in the plasma sheet boundary layer and lobe region, while in the plasma sheet, they traverse along arbitrary directions with respect to the magnetic field. Our study contributes to a deeper understanding of the complex electron dynamics under various plasma and magnetic field conditions within Earth's magnetotail.