Turbulence, Reconnection and Cosmic Rays in Galaxy Clusters

TL;DR

This paper reviews recent advances in understanding magnetic turbulence, reconnection, and cosmic ray acceleration in galaxy clusters, emphasizing the development of tested models and their implications for particle diffusion and acceleration.

Contribution

It summarizes current theories and observational insights into MHD turbulence, reconnection, and cosmic ray processes in galaxy clusters, highlighting recent progress and applications.

Findings

Turbulence reduces particle mean free path in galaxy clusters.

MHD turbulence models are now numerically validated.

Turbulence influences particle acceleration mechanisms.

Abstract

Recent years have been marked by substantial changes in our understanding of magnetic turbulence and magnetic reconnection, which, in its turn induced better understanding of cosmic ray diffusion and acceleration. Current models of magnetized turbulence are no more ad hoc constructions, but numerically tested theories. In this very short review we summarize topics presented in two talks given at the conference and provide a brief sketch of the vast and rapidly developing field. We discuss how turbulence decreases the efficient mean free path of the particles in the collisionless plasmas in galaxy clusters and claim that this makes MHD turbulence description applicable to a wider range of scales. We discuss the properties of MHD turbulence and its relation to magnetic reconnection. Finally, we overview how turbulence induces particle acceleration via second order Fermi process and affects first order Fermi acceleration in shocks and reconnection regions.