Turbulent reconnection acceleration

TL;DR

This paper investigates how turbulence in astrophysical plasmas influences magnetic reconnection and particle acceleration, revealing that turbulence-driven reconnection can efficiently accelerate particles with a non-universal spectral index.

Contribution

It introduces a model of particle acceleration during 3D turbulent reconnection driven by turbulence, highlighting the dependence of acceleration efficiency and spectral index on inflow speed and magnetic field configuration.

Findings

Particle acceleration efficiency increases with inflow speed.

Spectral index varies from approximately 2.5 to 4 depending on magnetic field conditions.

Reconnection acceleration can be highly efficient without scattering diffusion.

Abstract

The ubiquitous turbulence in astrophysical plasmas is important for both magnetic reconnection and reconnection acceleration. We study the particle acceleration during fast 3D turbulent reconnection with reconnection-driven turbulence. Particles bounce back and forth between the reconnection-driven inflows due to the mirror reflection and convergence of strong magnetic fields. Via successive head-on collisions, the kinetic energy of the inflows is converted into the accelerated particles. Turbulence not only regulates the inflow speed but also introduces various inflow obliquities with respect to the local turbulent magnetic fields. As both the energy gain and escape probability of particles depend on the inflow speed, the spectral index of particle energy spectrum is not universal. We find it in the range from $\approx 2.5$ to $4$, with the steepest spectrum expected at a strong guide field, i.e. a small angle between the total incoming magnetic field and the guide field. Without scattering diffusion needed for confining particles, the reconnection acceleration can be very efficient at a large inflow speed and a weak guide field.