"On the origin of the magnetic fields in the Universe: a dynamo in the accretion disks around black holes"
V.I. Pariev (Lebedev Physical Institute), S.A. Colgate
Abstract:
The energy of the magnetic field in large radiogalaxies is up to 10^{61} ergs. The most plausible source of this energy is the energy released when supermassive black holes were formed in almost every galaxy on the stage of active nuclei or quasars. Considerable ordered component of the magnetic field in the galaxy clusters can be deduced from the Faraday rotation measurements. We consider helical magnetic dynamo in accretion disks around supermassive black holes as a source for these large scale fields. In our model the kinetic helicity is of non-turbulent origin and is caused by the passages of the stars in the central stellar cluster through the accretion disk. We present results of the modelling of the magnetic dynamo and discuss the physics of star-disk collisions. Star-disk collisions produce significant kinetic helicity, which cannot be suppressed by the growing magnetic field. This is in contrast with the turbulent models of a large scale dynamo, such as alpha-omega dynamo in the mean field theory.