Theory of Global Disk Oscillations

Abstract

AbstractWe discuss the characteristics of global oscillation modes in Be disks and review recent studies related to the disk oscillation model. Since the m = 1 modes are present only in near Keplerian disks and the mode confinement occurs only in the region in which the radial flow is subsonic, the model of global disk oscillation strongly prefers the viscous decretion disk scenario proposed by Lee et al. (1991), whereas it is incompatible with the wind-compressed disk scenario of Bjorkman & Cassinelli (1993), which predicts angular-momentum conserving disks with supersonic radial flow. Based on the viscous decretion disk scenario, we discuss transonic solutions of decretion and examine the effect of viscosity on the global one-armed modes.