Tilt Dependence of Alignment in Accretion Disks Subjected to Lense--Thirring Torques

Abstract

We consider the effects of black hole tilt on accretion disk alignment, studying three initial black hole tilts,6 degrees, 12 degrees and 24 degrees, with both magnetohydrodynamic and (inviscid) hydrodynamic evolution. In a number of ways, but not all, the dynamics are homologous in the sense that the alignment fronts resulting from different initial tilts are very similar when analyzed in terms of the fraction of the initial tilt angle. Even when the initial misalignment is 24 degrees, which, for the sound speed studied, is 4 vertical scale heights at the disk fiducial radius, the surface density remains a smooth function of radius; i.e., we find no examples in which the disk inner aligned and outer misaligned regions separate, or "break".