Dynamics of Hot Accretion Flow with Thermal Conduction

TL;DR

This paper investigates how thermal conduction influences the dynamics of hot accretion flows around galactic nuclei, revealing that conduction cools and densifies the flow while affecting velocity and accretion rates.

Contribution

It introduces a self-similar unsteady solution to model hot accretion flows with thermal conduction, highlighting effects not captured by steady models.

Findings

Thermal conduction cools and densifies the accretion flow.

Conduction increases angular velocity and decreases radial infall velocity.

Mass accretion rate is reduced by thermal conduction.

Abstract

The purpose of this paper is to explore the dynamical behaviour of hot accretion flow with thermal conduction. The importance of thermal conduction on hot accretion flow is confirmed by observations of the hot gas that surrounds Sgr A$^*$ and a few other nearby galactic nuclei. In this research, the effect of thermal conduction is studied by a saturated form of it, as is appropriate for weakly collisional systems. The angular momentum transport is assumed to be a result of viscous turbulence and the $\alpha$-prescription is used for the kinematic coefficient of viscosity. The equations of accretion flow are solved in a simplified one-dimensional model that neglects the latitudinal dependence of the flow. To solve the integrated equations that govern the dynamical behaviour of the accretion flow, we have used an unsteady self-similar solution. The solution provides some insights into the dynamics of quasi-spherical accretion flow and avoids from limits of the steady self-similar solution. In comparison to accretion flows without thermal conduction, the disc generally becomes cooler and denser. These properties are qualitatively consistent with performed simulations in hot accretion flows. Moreover, the angular velocity increases with the magnitude of conduction, while the radial infall velocity decreases. The mass accretion rate onto the central object is reduced in the presence of thermal conduction. We found that the viscosity and thermal conduction have the opposite effects on the physical variables. Furthermore, the flow represents a transonic point that moves inward with the magnitude of conduction or viscosity.