Dynamo–generated turbulence and outflows from accretion discs

Local hydromagnetic simulations of accretion–disc turbulence currently provide the most convincing evidence that the origin of turbulence in discs could be the Balbus–Hawley magnetorotational instability. The main results of such calculations are highlighted with particular emphasis on the generation of large–scale magnetic fields. Comparison with mean–field dynamo theory is made. This theory is then used to address the question of the launching and collimation of winds emanating from the disc surfaces.