Origin and structure of electromagnetic generator regions at the edge of the electron diffusion region

Abstract

During the process of magnetic reconnection, converging magnetic fields transfer some of the stored magnetic energy into plasma energy. Simulations and spacecraft data suggest that at the edges of the electron diffusion region, “generators” can form where the local electromagnetic field gains energy from the plasma. We use a 2D Particle-in-cell (PIC) simulation and Magnetospheric Multiscale (MMS) spacecraft data to investigate the electron dynamics and energy budget of these generators. PIC simulation results suggest that these generators form where the electron population begins to remagnetize, while still not being fully frozen in to the magnetic fields. Super-Alfvénic electrons locally lose bulk kinetic energy to Hall electric fields along the outflow axis and to the out-of-plane reconnection electric field as they become remagnetized. These “partial” remagnetization regions also exhibit signatures of irreversible dissipation in MMS data, such as electron enthalpy flux and enhanced electron thermal energy density as remagnetized electrons scatter away from the neutral line within the Hall field structures of the exhaust.