Understanding Streaming Instabilities in the Limit of High Cosmic Ray Current Density
Abstract
A critical component of particle acceleration in astrophysical shocks is the non-resonant (Bell) instability, where the streaming of cosmic rays (CRs) leads to the amplification of magnetic fields necessary to scatter particles. In this work we use kinetic particle-in-cells simulations to investigate the high-CR current regime, where the typical assumptions underlying the Bell instability break down. Despite being more strongly driven, significantly less magnetic field amplification is observed compared to low-current cases, an effect due to the anisotropic heating that occurs in this regime. We also find that electron-scale modes, despite being fastest growing, mostly lead to moderate electron heating and do not affect the late evolution or saturation of the instability.
Keywords
Cite
@article{arxiv.2411.05704,
title = {Understanding Streaming Instabilities in the Limit of High Cosmic Ray Current Density},
author = {Emily Lichko and Damiano Caprioli and Benedikt Schroer and Siddhartha Gupta},
journal= {arXiv preprint arXiv:2411.05704},
year = {2025}
}