Seed magnetic fields in turbulent small-scale dynamos
  Magnetic fields in galaxies and galaxy clusters are amplified from a very
weak seed value to the observed $\mu{\rm G}$ strengths by the turbulent dynamo.
The seed magnetic field can be of primordial or astrophysical origin. The
strength and structure of the seed field, on the galaxy or galaxy cluster
scale, can be very different, depending on the seed-field generation mechanism.
The seed field first encounters the small-scale dynamo, thus we investigate the
effects of the strength and structure of the seed field on the small-scale
dynamo action. Using numerical simulations of driven turbulence and considering
three different seed-field configurations: 1) uniform field, 2) random field
with a power-law spectrum, and 3) random field with a parabolic spectrum, we
show that the strength and statistical properties of the dynamo-generated
magnetic fields are independent of the details of the seed field. We
demonstrate that, even when the small-scale dynamo is not active, small-scale
magnetic fields can be generated and amplified linearly due to the tangling of
the large-scale field. In the presence of the small-scale dynamo action, we
find that any memory of the seed field for the non-linear small-scale dynamo
generated magnetic fields is lost and thus, it is not possible to trace back
seed-field information from the evolved magnetic fields in a turbulent medium.
