Turbulent diffusion and galactic magnetism
  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.
