Joint Astrophysics Colloquium

MHD Turbulence and Transport in Accretion Disks

Jim Stone

Princeton University

In most astrophysical accretion disks, angular momentum transport and accretion is thought to be mediated by MHD turbulence driven by the magnetorotational instability (MRI). A number of recent numerical MHD studies of the MRI will be described, including new studies that investigate what determines the saturation amplitude (and therefore the mass accretion rate) in disks. I will show that anisotropic viscosity and thermal conduction in very diffuse accretion flows (such as around the black hole at the galactic center) has a significant effect on the MRI and turbulence in the disk: for example, it keeps the electron to ion temperature ratio close to one, which has important implications for the emssion properties of low-luminosity accretion flows.