Supernova-driven Turbulence and Magnetic Field Amplification in Disk
  Galaxies
  Supernovae are known to be the dominant energy source for driving turbulence
in the interstellar medium. Yet, their effect on magnetic field amplification
in spiral galaxies is still poorly understood. Analytical models based on the
uncorrelated-ensemble approach predicted that any created field will be
expelled from the disk before a significant amplification can occur. By means
of direct simulations of supernova-driven turbulence, we demonstrate that this
is not the case. Accounting for vertical stratification and galactic
differential rotation, we find an exponential amplification of the mean field
on timescales of 100Myr. The self-consistent numerical verification of such a
"fast dynamo" is highly beneficial in explaining the observed strong magnetic
fields in young galaxies. We, furthermore, highlight the importance of rotation
in the generation of helicity by showing that a similar mechanism based on
Cartesian shear does not lead to a sustained amplification of the mean magnetic
field. This finding impressively confirms the classical picture of a dynamo
based on cyclonic turbulence.
