  Recent work on the structure of magnetic fields in a turbulent medium gives
predictions for the properties of the magnetic flux tubes as a function of the
Mach number and scale of the turbulence, and the resistivity and viscosity of
the fluid. Here I discuss the implications of this work for accretion disks. I
show that although accretion disk flux tubes are usually almost completely
evacuated, they are nevertheless less buoyant than previous estimates have
suggested. I also note that vertical magnetic flux tends to be ejected from the
outer edge of accretion disks, so evidence for continued magnetic activity in
such systems should be interpreted as supporting the existence of dynamo
activity.

Astrophysics