The statistical research on the Kinetic- scale magnetic hole in magnetosheath

Kinetic- scale magnetic hole (KSMH) is a kind of structure whose spatial scale is only or smaller than the ion gyroradius and the magnetic field intensity shows rapid decrease in the observation. Recently, with the improvement of high spatio-temporal resolution measurements, previous studies have revealed some physical processes at the small scale, like electron energization, energy dissipation, wave-particle interaction and the turbulence. However, these studies on KSMHs have not touched on the generation and evolution of these structures due to limitations in the analysis methods used. In this work, using a series of KSMHs events observed by MMS and a new method to analyze the size of the hole, we are studying the relationship between the size of KSMHs and their spatial position in the magnetosheath statistically, and try to find the headstream of this type of structures and reveal their evolution process when they propagate with plasma flow.