Efficient Nonthermal Particle Acceleration by the Kink Instability in Relativistic Jets

TL;DR

This paper introduces a new particle acceleration mechanism in relativistic jets driven by kink instability, efficiently converting magnetic energy into nonthermal particles and explaining observed high-energy emissions.

Contribution

The study demonstrates, through large-scale simulations, that kink instability can produce power-law particle spectra and accelerate particles to ultra-high energies in astrophysical jets.

Findings

Formation of tangled magnetic fields promotes rapid particle energization.

Power-law energy distributions extend to radiation-reaction limits for leptons.

Mechanism accounts for observed spectra and ultra-high-energy cosmic rays.

Abstract

Relativistic magnetized jets from active galaxies are among the most powerful cosmic accelerators, but their particle acceleration mechanisms remain a mystery. We present a new acceleration mechanism associated with the development of the helical kink instability in relativistic jets, which leads to the efficient conversion of the jet's magnetic energy into nonthermal particles. Large-scale three-dimensional ab initio simulations reveal that the formation of highly tangled magnetic fields and a large-scale inductive electric field throughout the kink-unstable region promotes rapid energization of the particles. The energy distribution of the accelerated particles develops a well-defined power-law tail extending to the radiation-reaction limited energy in the case of leptons, and to the confinement energy of the jet in the case of ions. When applied to the conditions of well-studied bright knots in jets from active galaxies, this mechanism can account for the spectrum of synchrotron and inverse Compton radiating particles, and offers a viable means of accelerating ultra-high-energy cosmic rays to $10^{20}$ eV.