Turbulent diffusion and galactic magnetism

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.

2 pages, 1 figure, to appear in "Magnetic Fields in Diffuse Media", proceedings of Joint Discussion at the 2009 XXVII IAU General Assembly in Rio de Janeiro from 12 to 14 August, 2009