Résumé du preprint Irfu-09-25

Direct numerical simulations of the galactic dynamo in the kinematic growing phase
Gissinger,C., Fromang,S. & Dormy,E.
We present kinematic simulations of a galactic dynamo model based on the large scale differential rotation and the small scale helical fluctuations due to supernovae 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 superbubbles 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 observed. Moreover, our simulations show that the gravitational inflow plays an essential role to increase the magnetic growth rate. This observation appears to confirm the important role of the galactic fountain in sustaining galactic magnetic fields.