Magnetic fields and precession in accretion disks

We discuss tentative evidence for magnetic flux concentration in accretion disks. It derives from analysis of magnetically driven winds, missing radiation from inner disk parts and dwarf nova oscillations in cataclysmic variable systems and the precession period of the galactic black hole binary GRO 1655. We show that the evidence supports the notion that magnetic flux imposed on the disk from the surrounding magnetosphere of the secondary star becomes advectively concentrated to values that allow the acceleration of strong winds, significantly extract energy from the disk and could lead to a tilting instability of inner parts of the accretion disk.