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Dynamics of hot accretion flow with thermal conduction

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E-mail: kfaghei@du.ac.ir

ABSTRACT

The purpose of this paper is to explore the dynamical behaviour of hot accretion flows with thermal conduction. The importance of thermal conduction in hot accretion flows 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 through a saturated form, as is appropriate for weakly collisional systems. The angular momentum transport is assumed to be a result of viscous turbulence and the α-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 the limits of the steady self-similar solution. In comparison with accretion flows without thermal conduction, the disc generally becomes cooler and denser. These properties are qualitatively consistent with simulations performed in hot accretion flows. Moreover, the angular velocity increases with the magnitude of conduction, while the radial infall velocity decreases. The mass accretion rate on to the central object is reduced in the presence of thermal conduction. We found that viscosity and thermal conduction have opposite effects on the physical variables. Furthermore, the flow represents a transonic point that displaces inward with the magnitude of conduction or viscosity.

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