Particle dynamics in the electron current layer in collisionless magnetic reconnection

TL;DR

This study uses particle-in-cell simulations to reveal new electron orbit classes in collisionless magnetic reconnection, elucidating their role in jet dynamics and energetic electron distribution.

Contribution

It introduces novel classes of electron orbits in the electron current layer, enhancing understanding of particle behavior in magnetic reconnection.

Findings

Discovered figure-eight-shaped regular orbits inside the electron jet.

Identified noncrossing Speiser orbits and nongyrotropic electrons downstream.

Linked super-Alfvénic outflow jets to ensembles of Speiser orbits.

Abstract

Particle dynamics in the electron current layer in collisionless magnetic reconnection is investigated by using a particle-in-cell simulation. Electron motion and velocity distribution functions are studied by tracking self-consistent trajectories. New classes of electron orbits are discovered: figure-eight-shaped regular orbits inside the electron jet, noncrossing regular orbits on the jet flanks, noncrossing Speiser orbits, and nongyrotropic electrons in the downstream of the jet termination region. Properties of a super-Alfv\'{e}nic outflow jet are attributed to an ensemble of electrons traveling through Speiser orbits. Noncrossing orbits are mediated by the polarization electric field near the electron current layer. The noncrossing electrons are found to be non-negligible in number density. The impact of these new orbits to electron mixing, spatial distribution of energetic electrons, and observational signatures, is presented.