Viscous-Resistive ADAF with a general Large-Scale Magnetic Field

TL;DR

This study models hot accretion flows with large-scale magnetic fields, incorporating magnetic resistivity and a realistic viscosity model, revealing effects on disk velocities, thickness, and magnetic field influence.

Contribution

It introduces a self-consistent model of viscous-resistive ADAFs with a general magnetic field, considering variable viscosity and magnetic diffusivity influenced by magnetic fields.

Findings

Magnetic resistivity increases radial infall velocity and disk thickness.

Rotational velocity decreases with magnetic resistivity, but can become super-Keplerian.

All magnetic field components significantly affect disk structure and velocities.

Abstract

We have studied the structure of hot accretion flow bathed in a general large-scale magnetic field. We have considered magnetic parameters $ \beta_{r,\varphi,z}[=c^2_{r,\varphi,z}/(2c^2_{s})] $, where $ c^2_{r, \varphi, z} $ are the Alfv\'{e}n sound speeds in three direction of cylindrical coordinate $ (r,\varphi,z) $. The dominant mechanism of energy dissipation is assumed to be the magnetic diffusivity due to turbulence and viscosity in the accretion flow. Also, we adopt a more realistic model for kinematic viscosity $ (\nu=\alpha c_{s} H) $, with both $ c_{s} $ and $ H $ as a function of magnetic field. As a result in our model, the kinematic viscosity and magnetic diffusivity $ (\eta=\eta_{0}c_{s} H) $ are not constant. In order to solve the integrated equations that govern the behavior of the accretion flow, a self-similar method is used. It is found that the existence of magnetic resistivity will increase the radial infall velocity as well as sound speed and vertical thickness of the disk. However the rotational velocity of the disk decreases by the increase of magnetic resistivity. Moreover, we study the effect of three components of global magnetic field on the structure of the disk. We found out that the radial velocity and sound speed are Sub-Keplerian for all values of magnetic field parameters, but the rotational velocity can be Super-Keplerian by the increase of toroidal magnetic field. Also, Our numerical results show that all components of magnetic field can be important and have a considerable effect on velocities and vertical thickness of the disk.