2004A&A...423L..29D

The occurrence of the magnetorotational instability (MRI) in vertically stratified galactic disks is considered. Global 3D nonlinear MHD simulations with the ZEUSMP code are performed in a cylindric computational domain. Due to the evolution of the MRI toroidal and poloidal components of the mean magnetic fields are generated. The results are also applied to very young galaxies which are assumed to possess strong magnetic fields already after a few 10⁸ years. The dependence of MRI growth rate on the shear strength is shown. The velocity dispersion grows with height and reaches values of about 5km/s in good agreement with observations and close to the predictions of Sellwood & Balbus (1999ApJ...511..660S). For strong magnetic fields the MRI is suppressed but it is not suppressed by turbulence initially present in the disk.