Direct numerical simulations of the galactic dynamo in the kinematic
  growing phase
  We present kinematic simulations of a galactic dynamo model based on the
large scale differential rotation and the small scale helical fluctuations due
to supernova explosions. We report for the first time direct numerical
simulations of the full galactic dynamo using an unparameterized global
approach. We argue that the scale of helicity injection is large enough to be
directly resolved rather than parameterized. While the actual superbubble
characteristics can only be approached, we show that numerical simulations
yield magnetic structures which are close both to the observations and to the
previous parameterized mean field models. In particular, the quadrupolar
symmetry and the spiraling properties of the field are reproduced. Moreover,
our simulations show that the presence of a vertical inflow plays an essential
role to increase the magnetic growth rate. This observation could indicate an
important role of the downward flow (possibly linked with galactic fountains)
in sustaining galactic magnetic fields.
