The Speed of Cooling Fronts and the Functional form of the Dimensionless Viscosity in Accretion Disks

We examine the speed of inward-traveling cooling fronts in accretion disks. We show that their speed is determined by the rarefaction wave that precedes them and is approximately αFcF(H/r)q, where αF is the dimensionless viscosity, cF is the sound speed, r is the radial coordinate, H is the disk thickness, and all quantities are evaluated at the cooling front. The scaling exponent q lies in the interval [0, 1], depending on the slope of the (T, …