Ion-electron instabilities in the precursor of weakly magnetized, transrelativistic shocks

TL;DR

This paper investigates ion-electron instabilities in the precursor regions of weakly magnetized, transrelativistic shocks, highlighting the growth of specific wave modes and the conditions influencing large-scale electromagnetic instability development.

Contribution

It provides new insights into the properties and growth conditions of electrostatic and electromagnetic instabilities in relativistic shock precursors, including overlooked ion-electron modes.

Findings

Oblique Buneman waves grow significantly in relativistic regimes.

Secondary ion-electron instabilities are prominent in the precursor.

Electron pre-heating may enable large-scale filamentation modes.

Abstract

Collisionless shocks are known to induce turbulence via upstream ion reflection within the precursor region. This study elucidates the properties of electrostatic and electromagnetic instabilities, exploring their role over the transrelativistic range. Notably, the growth of oblique Buneman waves and previously overlooked, secondary small-scale ion-electron instabilities is observed to be particularly promoted in the relativistic regime. Furthermore, the growth of large-scale electromagnetic modes encounters severe limitations in any cold, baryon-loaded precursor. It is argued that electron pre-heating in electrostatic modes may alleviate these constraints, facilitating the subsequent growth of large-scale filamentation modes in the precursor of transrelativistic shocks.