Anatomy and Physiology of Precessing Accretion Disks

Julian Krolik

May 09, 2013

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Abstract: Accretion disks form in an extremely wide variety of contexts, from proto-stellar systems to active galactic nuclei. In many cases, the matter feeding them has angular momentum oblique to the angular momentum of the central gravitating object, whether it is a binary system or a spinning black hole. When that happens, the orbiting matter precesses around the central object’s angular momentum axis with a rate that grows rapidly faster toward the central object. It is generally thought that somewhere sufficiently close to the center frictional forces will drive the disk’s orbital angular momentum into alignment with the central object’s angular momentum. In this talk I will present the first calculation showing how this happens when the internal stresses in the matter, rather than being modeled phenomenologically, have a clear physical origin: hydrodynamics and MHD turbulence.