THE GRAVITOMAGNETIC DYNAMO EFFECT IN ACCRETION DISKS OF ROTATING BLACK-HOLES

We present a previously unknown dynamo effect that arises from the coupling of the gravitomagnetic held of a Kerr black hole with electromagnetic fields. The axisymmetric dynamo equations are derived in the 3 + 1 split of Kerr spacetime. They are formally identical to their equivalents in flat space, augmented by a general relativistic source term for the poloidal magnetic field provided by the gravitomagnetic held. There is no need for any particular small-scale plasma motions. The effect does, however, require finite conductivity and is enhanced by anaomalous or turbulent magnetic diffusivity. The results of our time-dependent numerical simulations of the mean field dynamo in a turbulent accretion disk prove that the gravitomagnetic dynamo has growing modes in the vicinity of a rotating black hole.