Particle-acceleration mechanisms in multispecies relativistic plasmas

TL;DR

This study investigates particle acceleration in multispecies relativistic plasmas, revealing how reconnection-driven electric fields energize particles differently based on plasma composition, with implications for astrophysical phenomena.

Contribution

First comprehensive analysis of particle acceleration mechanisms in kinetic, relativistic turbulence with realistic electron, positron, and proton mass ratios.

Findings

Energization occurs at reconnection current sheets driven by pressure tensor divergence.

Imbalance between electrons and positrons favors electron acceleration.

Realistic multispecies modeling is crucial for understanding nonthermal emissions in astrophysical jets.

Abstract

While collisionless plasmas are ubiquitously present near astrophysical compact objects, the impact that their composition has on the high-energy emission is presently unknown. We present the first investigation of particle-acceleration mechanisms in kinetic, special-relativistic turbulence, modeling electrons, positrons, and protons with realistic mass ratios. Under global charge neutrality, we introduce a positron fraction and cover regimes ranging from an electron-proton plasma over to pair-dominated plasmas. Using a novel generalized Ohm's law for multispecies relativistic plasmas, we analyze particle acceleration due to electric fields in reconnection events that self-consistently emerge from turbulence. We demonstrate, for the first time, that energization occurs at reconnection current sheets driven by the divergence of the relativistic pressure tensor, which locally aligns with the particle velocity and leads to an efficient energy transfer. The imbalance between electrons and positrons systematically favors electron acceleration, highlighting the necessity of realistic multispecies modeling to capture the nonthermal contributions in accretion flows and relativistic jets from black holes.