Energy transfer and electron energization in collisionless magnetic reconnection for different guide-field intensities

TL;DR

This study uses 2D full-particle simulations to analyze how guide-field intensity influences energy transfer and electron energization during collisionless magnetic reconnection, confirming experimental observations and exploring heating mechanisms.

Contribution

It provides new insights into the dependence of energy conversion regimes and electron heating mechanisms on guide-field strength in collisionless reconnection.

Findings

Energy transfer shifts from parallel to perpendicular dominance with increasing guide field.

No significant variation in energy partition among species across different guide fields.

Electron perpendicular heating mechanisms are examined through distribution functions and particle orbits.

Abstract

Electron dynamics and energization are one of the key components of magnetic field dissipation in collisionless reconnection. In 2D numerical simulations of magnetic reconnection, the main mechanism that limits the current density and provides an effective dissipation is most probably the electron pressure tensor term, that has been shown to break the frozen-in condition at the x-point. In addition, the electron-meandering-orbit scale controls the width of the electron dissipation region, where the electron temperature has been observed to increase both in recent Magnetospheric Multiple-Scale (MMS) observations as well as in laboratory experiments, such as the Magnetic Reconnection Experiment (MRX). By means of two-dimensional full-particle simulations in an open system, we investigate how the energy conversion and particle energization depend on the guide field intensity. We study the energy transfer from magnetic field to the plasma, ${\bf E}\cdot {\bf J}$ and the threshold guide field separating two regimes where either the parallel component, $E_{||}J_{||}$, or the perpendicular component, ${\bf E}_{\perp}\cdot {\bf J}_{\perp}$, dominate the energy transfer, confirming recent MRX results and also consistent with MMS observations. We calculate the energy partition between fields, kinetic, and thermal energy of different species, from electron to ion scales, showing there is no significant variation for different guide field configurations. Finally we study possible mechanisms for electron perpendicular heating by examining electron distribution functions and self-consistently evolved particle orbits in high guide field configurations.