Magnetic torque on a charged rotating black hole

An asymptotically uniform weak magnetic field exerts a torque on a black hole equal to the cross product of its asymptotic limit and the magnetic moment of the black hole. As this torque on the intrinsic dipole moment can be much stronger than the torque exerted on the dipole moment induced by the magnetic field, a charged black hole might influence the inner region of its accretion disk magnetically. 'Larmor' precession of test charge orbits can be much stronger than Lense-Thirring precession, but is unlikely to be dominant in the middle region of a conventional stationary accretion disk. A magnetic field that would cause a solar-mass (supermassive) black hole to precess with a period of less than a month (thousand years) could not be supported by a stationary accretion disk. (orig.)