The role of non-linear Landau damping for cosmic-ray transport

TL;DR

This paper investigates how non-linear Landau damping influences cosmic-ray scattering in high beta plasma, revealing plasma heating, reduced CR drift speed, and an inverse cascade producing large-scale modes, with implications for galactic CR transport.

Contribution

First assessment using hybrid PIC simulations showing non-linear Landau damping's effects on cosmic-ray scattering and inverse cascade in high beta plasma.

Findings

Plasma heating due to damping

Reduction of CR drift speed while remaining super-Alfvenic

Generation of non-resonant large-scale modes

Abstract

We present the first assessment, using hybrid PIC simulations, of the role of non-linear Landau damping in the process of self-generated scattering in a high $\beta$ plasma, conditions appropriate for CR scattering in the halo of the Galaxy. This damping process manifests itself in the form of heating of the background plasma and reduction of the drift speed of CRs that yet remains super-Alfvenic. We also show that the damping leads to an inverse cascade process, consisting of producing non-resonant large scale modes, a novel result with many potential phenomenological implications.