FLOW AND DISTRIBUTION OF MAGNETIC ENERGY IN ACCRETION DISKS - A KINEMATIC APPROACH

By taking account of the statistical nature of kinematic mean field dy namo theory, it is pointed out that the mean magnetic field [B] should always vanish. A more fruitful approach therefore seems to be to stud y the dynamics of the second moment [BB] of magnetic field which conta ins information on mean magnetic energy and statistical correlations b etween the various components of the magnetic field. The general dynam ics of this tensor are discussed. As an application a stationary solut ion for zero helicity is presented in a local approximation. It is fou nd that such a dynamo can only be maintained by compressible turbulenc e. The implications of this nonhelical solution for the structure and emission of stationary thin accretion disks are discussed. The limits of applicability of the kinematic approach are briefly discussed. We a pply our model to the inner region of the accretion disk around the bl ack hole candidate LMC X-3. We find typical rms magnetic field strengt h values in the range 4 x 10(6) - 4 x 10(7) Gauss.