Sub‐Structures of the Separatrix Region During Magnetic Reconnection

Abstract

AbstractUtilizing data from the Magnetospheric Multiscale mission, the sub‐structures of the separatrix region during reconnection are investigated. A small current system in the separatrix region is embedded in the large Hall current system, which appears as a quadrupole current. This small current system has an opposite direction to the Hall current and cancels part of the Hall magnetic field. The formation of the quadrupole current is possibly related to the patchy parallel electric field. The electric field in the separatrix region can be divided into three sub‐layers according to the electron frozen‐in condition. En enhances in two outside sub‐layers, where the strong En is supported by the Hall term and electron pressure gradient term, and the nearly zero En, separating the enhanced electric fields, is caused by a small flow and electron density gradient. Our observations imply complex dynamics in the separatrix region during magnetic reconnection.