Magnetically Driven Warping and Precession of Accretion Disks: Implications for "Exotic" Stellar Variabilities

Abstract

The inner region of the accretion disk around a magnetized star is subjected to magnetic torques that induce warping and precession of the disk. These torques arise from interactions between the stellar field and the induced electric currents in the disk. These novel magnetic effects give rise to some ``exotic'' stellar variabilities, and may play an important role in explaining a number of puzzling behaviors related to disk accretion onto magnetic stars, such as mHz QPOs in X-ray pulsars, long-term periodicities of X-ray binaries (including precession of jets), low-Frequency (10-50 Hz) QPO's in low-mass X-ray binaries, and photometric variabilities of T Tauri stars.