Stochastic reacceleration of relativistic electrons by turbulent reconnection: a mechanism for cluster-scale radio emission ?

TL;DR

This paper explores a novel mechanism where relativistic electrons are reaccelerated by turbulent reconnection in galaxy clusters, potentially explaining diffuse radio emissions through large-scale turbulence effects.

Contribution

It introduces a new physical model for electron reacceleration in galaxy clusters based on turbulent reconnection and large-scale turbulence, extending previous numerical studies.

Findings

Proposes a stochastic reacceleration mechanism involving turbulent reconnection.

Suggests this process can account for cluster-scale diffuse radio emission.

Highlights the role of large-scale incompressible turbulence in particle acceleration.

Abstract

In this paper we investigate a situation where relativistic particles are reaccelerated diffusing across regions of reconnection and magnetic dynamo in super-Alfvenic, incompressible large-scale turbulence. We present an exploratory study of this mechanism in the intra-cluster-medium (ICM). In view of large-scale turbulence in the ICM we adopt a reconnection scheme that is based on turbulent reconnection and MHD turbulence. In this case particles are accelerated and decelerated in a systematic way in reconnecting and magnetic-dynamo regions, respectively, and on longer time-scales undergo a stochastic process diffusing across these sites (similar to second-order Fermi). Our study extends on larger scales numerical studies that focused on the acceleration in and around turbulent reconnecting regions. We suggest that this mechanism may play a role in the reacceleration of relativistic electrons in galaxy clusters providing a new physical scenario to explain the origin of cluster-scale diffuse radio emission. Indeed differently from current turbulent reacceleration models proposed for example for radio halos this mechanism is based on the effect of large-scale incompressible and super-Alfvenic turbulence. In this new model turbulence governs the interaction between relativistic particles and magnetic field lines that diffuse, reconnect and are stretched in the turbulent ICM.