EFFECT OF ADVECTED FIELDS ON ACCRETION DISK DYNAMOS

We present calculations of favored dynamo modes when advection of ambi ent magnetic fields onto accretion disks is important. These models ar e relevant for compact binary systems and young stellar objects and ca n be extended to active galactic nuclei (AGNs). The dynamo equation, i ncluding the standard alpha-effect, is modified to take into account a dvected magnetic fields. Vacuum boundary conditions are assumed outsid e the disk and the dynamo number switches sign across the equatorial p lane. For the local steady state problem, critical dynamo numbers for various modes are obtained analytically. Our motivation is to investig ate whether the dominant dynamo generation of quadrupolar magnetic fie lds and accretion of dipolar magnetic fields is likely to lead to part icle acceleration in the form of jets. The results shown here are for a particular choice of boundary conditions and geometry of the advecte d field. Besides examining other choices, we shall calculate growth ra tes for different modes, and the influence of the initial seed field c onfiguration on the evolution of the magnetic fields in subsequent wor k.