Confining the high-energy cosmic rays

TL;DR

This paper investigates the instabilities affecting the confinement of high-energy cosmic rays in supernova remnant shock regions, crucial for understanding their acceleration via diffusive shock acceleration.

Contribution

It analyzes a specific instability acting on scales larger than the cosmic ray gyroradius, providing insights into its driving mechanism and growth times.

Findings

Identification of an instability on large scales affecting cosmic ray confinement

Analysis of the instability's driving mechanism

Estimation of the growth times of the instability

Abstract

Diffusive shock acceleration is the prime candidate for efficient acceleration of cosmic rays. Galactic cosmic rays are believed to originate predominantly from this process in supernova remnant shock waves. Confinement of the cosmic rays in the shock region is key in making the mechanism effective. It has been known that on small scales (smaller than the typical gyroradius) high-amplitude non-resonant instabilities arise due to cosmic ray streaming ahead of the shock. For the efficiency of scattering of the highest energy cosmic rays it is of interest to determine the type of instabilities that act on longer length scales, i.e. larger than the cosmic ray gyroradius. We will present the results of our analysis of an instability that acts in this regime and will discuss its driving mechanism and typical growth times.