Kinetic simulations of magnetic reconnection in presence of a background O+ population

TL;DR

This study uses particle-in-cell simulations to explore how background O+ ions influence magnetic reconnection, revealing effects on reconnection rate, magnetic field structure, ion separation, and guide field dynamics.

Contribution

It provides new insights into the role of O+ ions in magnetic reconnection, highlighting their impact on reconnection rate, magnetic field structures, and ion behavior.

Findings

O+ ions slightly decrease the reconnection rate

Hall magnetic field shows a two-scale structure with O+ presence

O+ ions initially separate in the outflow region

Abstract

Particle-in-Cell simulations of magnetic reconnection with an H+ current sheet and a mixed background plasma of H+ and O+ ions are completed using physical mass ratios. Four main results are shown. First, the O+ presence slightly decreases the reconnection rate and the magnetic reconnection evolution depends mainly on the lighter H+ ion species in the presented simulations. Second, the Hall magnetic field is characterized by a two-scale structure in presence of O+ ions: it reaches sharp peak values in a small area in proximity of the neutral line, and then decreases slowly over a large region. Third, the two background species initially separate in the outflow region because H+ and O+ ions are accelerated by different mechanisms occurring on different time scales and with different strengths. Fourth, the effect of a guide field on the O+ dynamics is studied: the O+ presence does not change the reconnected flux and all the characteristic features of guide field magnetic reconnection are still present. Moreover, the guide field introduces an O+ circulation pattern between separatrices that enhances high O+ density areas and depletes low O+ density regions in proximity of the reconnection fronts. The importance and the validity of these results are finally discussed.