Effects of Power-Law Cooling in Viscous Flows

Abstract

We carry out a series of numerical simulations of viscous accretion flows having a reasonable spatial distribution of the viscosity parameter. We add the power-law cooling throughout the flow. We show that in agreement with the theoretical solutions of viscous transonic flows, matter having viscosity parameter above a critical value becomes a Keplerian disc while matter having lesser viscosity remains a low angular momentum, sub-Keplerian flow. The latter component produces centrifugal pressure supported shock waves. Thus, for instance, flows having sufficiently high viscosity on the equatorial plane and low viscosity above and below, produce a Two Component Advective Flow (TCAF), where a Keplerian disc is surrounded by a rapidly moving sub-Keplerian halo. We find that the post-shock region of the Keplerian disc is evaporated and the configuration is stable. This agrees with the theoretical models which attempt to explain the spectral and timing properties of black hole candidates.