Magnetic fields and shock waves in cluster outskirts

TL;DR

This paper explores magnetic fields and shock waves in galaxy cluster outskirts, emphasizing recent radio relic discoveries, their implications for particle acceleration, and insights from MHD simulations on magnetic field origins.

Contribution

It presents MHD simulations addressing the origin of magnetic fields in cluster outskirts and discusses the implications of radio relic observations for understanding shock waves.

Findings

Radio relic polarisation reveals magnetic field topology.

Simulations highlight challenges in explaining magnetic field origins.

Observations suggest active particle acceleration in cluster outskirts.

Abstract

Both, X-ray and radio observations, are beginning to probe regions in galaxy clusters close to the virial radius. These are particularly interesting regions as they are (i) crucial for the thermal evolution of the intra-cluster medium and (ii) they host plasmas under conditions that are poorly understood. Recently discovered giant radio relics in the galaxy cluster CIZA J2242.8+5301 provide unprecedented evidence for particle acceleration in cluster outskirts. We will discuss some of the intriguing puzzles that surround these relics. The polarisation of the radio emission yields information about the topology of magnetic fields in these shock waves. Here we report on MHD simulations that highlight some problems about the origin of these magnetic fields.