  Within the interstellar medium, supernovae are thought to be the prevailing
agents in driving turbulence. Until recently, their effects on magnetic field
amplification in disk galaxies remained uncertain. Analytical models based on
the uncorrelated-ensemble approach predicted that any created field would be
expelled from the disk before it could be amplified significantly. By means of
direct simulations of supernova-driven turbulence, we demonstrate that this is
not the case. Accounting for galactic differential rotation and vertical
stratification, we find an exponential amplification of the mean field on
timescales of several hundred million years. We especially 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.
