Efficient Nonthermal Ion and Electron Acceleration Enabled by the Flux-Rope Kink Instability in 3D Nonrelativistic Magnetic Reconnection

TL;DR

This paper shows that flux-rope kink instability in 3D magnetic reconnection enhances particle acceleration by creating chaos, enabling ions and electrons to develop power-law energy spectra relevant to space and astrophysical observations.

Contribution

It demonstrates that flux-rope kink instability induces chaos in magnetic reconnection, significantly improving particle acceleration efficiency in 3D kinetic simulations.

Findings

Particles develop power-law energy spectra with significant energy fraction.

Chaos allows particles to escape flux-ropes and undergo further acceleration.

High-energy cutoffs scale with system size.

Abstract

The relaxation of field-line tension during magnetic reconnection gives rise to a universal Fermi acceleration process involving the curvature drift of particles. However, the efficiency of this mechanism is limited by the trapping of energetic particles within flux-ropes. Using 3D fully kinetic simulations, we demonstrate that the flux-rope kink instability leads to strong field-line chaos in weak-guide-field regimes where the Fermi mechanism is most efficient, thus allowing particles to transport out of flux-ropes and undergo further acceleration. As a consequence, both ions and electrons develop clear power-law energy spectra which contain a significant fraction of the released energy. The low-energy bounds are determined by the injection physics, while the high-energy cutoffs are limited only by the system size. These results have strong relevance to observations of nonthermal particle acceleration in space and astrophysics.