2008ApJ...683..949L

The accretion disk around a rotating magnetic star (neutron star, white dwarf, or T Tauri star) is subjected to periodic vertical magnetic forces from the star, with the forcing frequency equal to the stellar spin frequency or twice the spin frequency. This gives rise to bending waves in the disk that may influence the variabilities of the system. We study the excitation, propagation, and dissipation of these waves using a purely hydrodynamical model coupled with a generic model description of the magnetic forces. The m=1 bending waves are excited at the Lindblad/vertical resonance and propagate either to larger radii or inward toward the corotation resonance where dissipation takes place. While the resonant torque is negligible compared to the accretion torque, the wave nevertheless may reach an appreciable amplitude and can cause or modulate flux variabilities from the system. We discuss the possible relevance of our result to the observed quasi-periodic oscillations from various systems, in particular neutron star low-mass X-ray binaries.