The Variability of Active Galactic Nuclei and the Radial Transport of Vertical Magnetic Flux

We consider the radial buoyancy of vertical magnetic field lines in radiation- and gas-pressure–dominated accretion disks. We find that in addition to radial drift driven by turbulent diffusion and biased by the global field geometry, there are buoyancy effects which tend to move magnetic flux outward. In gas-pressure–dominated disks the poloidal magnetic field will move outward at a rate comparable to its inward advection. On the other hand, …