Magnetic field amplification by SN-driven interstellar turbulence

TL;DR

This study uses direct simulations to show that supernova-driven turbulence, combined with galactic rotation and stratification, can exponentially amplify magnetic fields in disk galaxies over hundreds of millions of years.

Contribution

It demonstrates through simulations that supernova-driven turbulence, coupled with galactic rotation, effectively amplifies magnetic fields, challenging previous analytical predictions.

Findings

Magnetic field amplification occurs exponentially over hundreds of millions of years.

Galactic rotation is crucial for generating helicity and sustaining magnetic field growth.

Cartesian shear alone does not sustain magnetic field amplification.

Abstract

Within the interstellar medium, supernovae are thought to be the prevailing agents in driving turbulence. Until recently, their effects on magnetic field amplification in disk galaxies remained uncertain. Analytical models based on the uncorrelated-ensemble approach predicted that any created field would be expelled from the disk before it could be amplified significantly. By means of direct simulations of supernova-driven turbulence, we demonstrate that this is not the case. Accounting for galactic differential rotation and vertical stratification, we find an exponential amplification of the mean field on timescales of several hundred million years. We especially highlight the importance of rotation in the generation of helicity by showing that a similar mechanism based on Cartesian shear does not lead to a sustained amplification of the mean magnetic field.