  Recent simulations of supernova-driven turbulence within the ISM support the
existence of a large-scale dynamo. With a growth time of about two hundred
million years, the dynamo is quite fast -- in contradiction to many assertions
in the literature. We here present details on the scaling of the dynamo effect
within the simulations and discuss global mean-field models based on the
adopted turbulence coefficients. The results are compared to global simulations
of the magneto-rotational instability.
