On the Cosmic Ray Driven Firehose Instability

TL;DR

This paper investigates the non-resonant firehose instability driven by cosmic rays in supernova remnant shock precursors, analyzing conditions for its operation and presenting preliminary simulation results.

Contribution

It introduces a tensor expansion approach to identify conditions for the firehose instability and provides initial simulation insights relevant to supernova shocks.

Findings

Linear firehose growth rate is marginally faster than resonant in fast shocks

Tensor expansion method clarifies instability conditions

Preliminary simulation results support theoretical predictions

Abstract

The role of the non-resonant firehose instability in conditions relevant to the precursors of supernova remnant shocks is considered. Using a second order tensor expansion of the Vlasov-Fokker-Planck equation we illustrate the necessary conditions for the firehose to operate. It is found that for very fast shocks, the diffusion approximation predicts that the linear firehose growth rate is marginally faster than its resonant counterpart. Preliminary hybrid MHD-Vlasov-Fokker-Planck simulation results using young supernova relevant parameters are presented.