A galaxy dynamo by supernova-driven interstellar turbulence

TL;DR

This paper demonstrates through simulations that supernova-driven turbulence can rapidly amplify magnetic fields in the interstellar medium, supporting the existence of a galactic dynamo mechanism.

Contribution

It provides the first self-consistent simulation evidence of a fast dynamo driven by supernova-induced turbulence in disk galaxies.

Findings

Exponential magnetic field amplification observed within a few hundred million years.

Sustained dynamo action at moderate magnetic Reynolds numbers.

Supernovae produce a turbulent alpha effect consistent with quasilinear theory.

Abstract

Supernovae are the dominant energy source for driving turbulence within the interstellar plasma. Until recently, their effects on magnetic field amplification in disk galaxies remained a matter of speculation. By means of self-consistent simulations of supernova-driven turbulence, we find an exponential amplification of the mean magnetic field on timescales of a few hundred million years. The robustness of the observed fast dynamo is checked at different magnetic Reynolds numbers, and we find sustained dynamo action at moderate Rm. This indicates that the mechanism might indeed be of relevance for the real ISM. Sensing the flow via passive tracer fields, we infer that SNe produce a turbulent alpha effect which is consistent with the predictions of quasilinear theory. To lay a foundation for global mean-field models, we aim to explore the scaling of the dynamo tensors with respect to the key parameters of our simulations. Here we give a first account on the variation with the supernova rate.