On the energisation of charged particles by fast magnetic reconnection

TL;DR

This paper investigates how turbulence influences magnetic reconnection and particle energisation using 3D simulations, revealing different scaling behaviors depending on turbulence intensity.

Contribution

It demonstrates the impact of turbulence on reconnection rates and particle energisation, highlighting a transition from Sweet-Parker scaling to turbulence-dominated behavior.

Findings

Reconnection rate follows Sweet-Parker scaling at low turbulence.

At high turbulence, reconnection rate becomes nearly independent of Lundquist number.

Particle energisation results in Maxwellian velocity distributions with variance scaling.

Abstract

We study the role of turbulence in magnetic reconnection, within the framework of magneto-hydrodynamics, using three-dimensional direct numerical simulations. For small turbulent intensity we find that the reconnection rate obeys Sweet-Parker scaling. For large enough turbulent intensity reconnection rate departs significantly from Sweet-Parker behaviour, becomes almost a constant as a function of the Lundquist number. We further study energisation of test-particles in the same setup. We find that the speed of the energised particles obeys a Maxwellian distribution, whose variance also obeys Sweet-Parker scaling for small turbulent intensity but depends weakly on the Lundquist number for large turbulent intensity. Furthermore, the variance is found to increase with the strength of the reconnecting magnetic field.