Turbulent diffusion and galactic magnetism

TL;DR

This paper investigates how turbulent magnetic diffusivity behaves in irrotational turbulence driven by spherical expansion waves, revealing it increases with magnetic Reynolds number and saturates at a certain level, impacting galactic dynamo models.

Contribution

It demonstrates the dependence of turbulent magnetic diffusivity on magnetic Reynolds number using the test-field method in irrotational turbulence, relevant for galactic magnetic field studies.

Findings

Magnetic diffusivity increases with Reynolds number

Diffusivity levels off at several times the rms velocity times wave radius

Implications for galactic mean-field dynamo models

Abstract

Using the test-field method for nearly irrotational turbulence driven by spherical expansion waves it is shown that the turbulent magnetic diffusivity increases with magnetic Reynolds numbers. Its value levels off at several times the rms velocity of the turbulence multiplied by the typical radius of the expansion waves. This result is discussed in the context of the galactic mean-field dynamo.