Cosmic-ray driven dynamo in galactic disks

TL;DR

This paper demonstrates that cosmic rays from supernova remnants can drive a galactic dynamo, amplifying magnetic fields through differential rotation, buoyancy, and resistive dissipation, leading to energy equipartition in galactic disks.

Contribution

It introduces new resistive CR-MHD simulations showing cosmic-ray driven dynamo action and energy equipartition in galactic magnetic fields.

Findings

Cosmic rays from supernova remnants can drive large-scale galactic dynamos.

The dynamo leads to magnetic field amplification on galactic timescales.

Energy equipartition is achieved among gas turbulence, magnetic fields, and cosmic rays.

Abstract

We present new developments on the Cosmic--Ray driven, galactic dynamo, modeled by means of direct, resistive CR--MHD simulations, performed with ZEUS and PIERNIK codes. The dynamo action, leading to the amplification of large--scale galactic magnetic fields on galactic rotation timescales, appears as a result of galactic differential rotation, buoyancy of the cosmic ray component and resistive dissipation of small--scale turbulent magnetic fields. Our new results include demonstration of the global--galactic dynamo action driven by Cosmic Rays supplied in supernova remnants. An essential outcome of the new series of global galactic dynamo models is the equipartition of the gas turbulent energy with magnetic field energy and cosmic ray energy, in saturated states of the dynamo on large galactic scales.