Accretion Disks with Convective Viscosity

Abstract

Models of vertical structure are calculated for a range of parameters applicable to dwarf novae with two types of viscosity being included: the standard α-disk viscosity and the additional turbulent viscosity in the convective regions. The resulting surface density (∑) υs. effective temperature (T_e) relations, compared to those without convective viscosity, show larger separation between the two critical points of the ∑ – T_e relation, ∑_min and ∑_max. This could suggest that with such a modification the dwarf nova outbursts could be reproduced with a single value of α. (Note that in the standard α approach two different α’s are needed on the hot and cool branch of the ∑ – T_e relation, with α_cool ≈ α_hot/4). It turns out, however, that this is not the case. This is due to the fact that additional convective viscosity makes also ∑_max smaller than in the pure α case.