Meridional circulation and reverse advection in hot thin accretion discs

Abstract

In standard accretion discs, outward angular momentum transfer by viscous forces is compensated by the inward motion of the accreting matter. However, the vertical structure of real accretion discs leads to meridional circulation with comparable amplitudes of poloidal velocities. Using thin-disc approximation, we consider different regimes of disc accretion with different vertical viscosity scalings. We show that, while gas-pressure-dominated discs can easily have a midplane outflow, standard thin radiation-pressure-dominated disc is normally moving inwards at all the heights. However, quasi-spherical scaling for pressure ($p\propto {\varpi }^{-5/2}$) leads to a midplane outflow for a very broad range of parameters. It particular, this may lead to a reversed, outward heat advection in geometrically thick discs when the temperature decreases rapidly enough with height. While the overall direction of heat advection depends on the unknown details of vertical structure and viscosity mechanisms, existence of the midplane counterflow in quasi-spherical flows is a robust result weakly dependent on the parameters and the assumptions of the model. Future models of thick radiatively inefficient flows should take meridional circulation into account.

arXiv comment13 pages, one figure; accepted to MNRAS

References in corpus (9)

• Hot Accretion Flows Around Black Holes
• Super-critically accreting stellar-mass black holes as ultraluminous X-ray sources
• Convection-Dominated Accretion Flows
• Enhanced Angular Momentum Transport in Accretion Disks
• Three-dimensional simulations of super-critical black hole accretion disks --- luminosities, photon trapping and variability
• Global simulations of axisymmetric radiative black hole accretion disks in general relativity with a sub-grid magnetic dynamo
• On the dynamics of magnetorotational turbulent stresses
• Meridional circulation in turbulent protoplanetary disks
• On angular momentum transport in convection-dominated accretion flows

Cited by in corpus (1)

• PATOKA: Simulating Electromagnetic Observables of Black Hole Accretion