A kinetic approach to non resonant modes and growth rates of streaming instability: consequences for shock acceleration

TL;DR

This paper introduces a kinetic method to analyze non-resonant wave modes and growth rates of streaming instability near shock fronts, revealing a rapidly growing mode similar to Bell's MHD results, with enhanced modeling flexibility.

Contribution

It presents a kinetic framework for studying cosmic ray-induced wave excitation, extending previous MHD-based findings and enabling exploration of various cosmic ray current compensation models.

Findings

Identification of a non-alfvenic fast-growing mode

Validation of Bell's MHD results using a kinetic approach

Enhanced understanding of cosmic ray current effects

Abstract

We show here that a purely kinetic approach to the excitation of waves by cosmic rays in the vicinity of a shock front leads to predict the appearance of a non-alfvenic fastly growing mode which is the same that was found by Bell (2004) by treating the plasma in the MHD approximation. The kinetic approach we present is more powerful in that it allows us to investigate different models for the compensation of the cosmic ray current in the background upstream plasma.