Mildly relativistic magnetized shocks in electron-ion plasmas -- II. Particle acceleration and heating

TL;DR

This study uses high-resolution simulations to explore how mildly relativistic magnetized shocks in electron-ion plasmas accelerate and heat particles, revealing the critical role of shock rippling in electron energization.

Contribution

First demonstration that shock rippling is essential for electron acceleration at mildly relativistic shocks in electron-ion plasmas.

Findings

Electrons are super-adiabatically heated at the shock.

Most energy transfer from protons to electrons occurs at or downstream of the shock.

Downstream electron spectra are approximately thermal with limited non-thermal components.

Abstract

Particle acceleration and heating at mildly relativistic magnetized shocks in electron-ion plasma are investigated with unprecedentedly high-resolution two-dimensional particle-in-cell simulations that include ion-scale shock rippling. Electrons are super-adiabatically heated at the shock, and most of the energy transfer from protons to electrons takes place at or downstream of the shock. We are the first to demonstrate that shock rippling is crucial for the energization of electrons at the shock. They remain well below equipartition with the protons. The downstream electron spectra are approximately thermal with a limited supra-thermal power-law component. Our results are discussed in the context of wakefield acceleration and the modelling of electromagnetic radiation from blazar cores.