Particle acceleration in kink-unstable jets

TL;DR

This study uses particle-in-cell simulations to investigate how kink instability in magnetized jets accelerates particles, revealing the roles of magnetic reconnection and turbulence in energizing particles in GRBs and AGNs.

Contribution

It provides the first-principles simulation analysis of kink instability in force-free jets, highlighting particle acceleration mechanisms involving reconnection and turbulence.

Findings

Kink instability leads to large-scale current sheets and turbulence.

Reconnection occurs in strong guide fields, producing steep particle spectra.

Plasma heating is driven by turbulence induced by the instability.

Abstract

Magnetized jets in GRBs and AGNs are thought to be efficient accelerators of particles, however, the process responsible for the acceleration is still a matter of active debate. In this work, we study the kink-instability in non-rotating force-free jets using first-principle particle-in-cell simulations. We obtain similar overall evolution of the instability as found in MHD simulations. The instability first generates large scale current sheets, which at later times break up into small-scale turbulence. Reconnection in these sheets proceeds in the strong guide field regime, which results in a formation of steep power laws in the particle spectra. Later evolution shows heating of the plasma, which is driven by small-amplitude turbulence induced by the kink instability. These two processes energize particles due to a combination of ideal and non-ideal electric fields.