Anchoring polar magnetic field in a stationary thick accretion disk

TL;DR

This paper analyzes the structure of hot, magnetized accretion disks with poloidal magnetic fields, revealing how magnetic symmetry influences disk thickness and accretion rates, and providing analytical solutions for magnetic flux.

Contribution

It introduces an analytical model for stationary thick accretion disks with poloidal magnetic fields, highlighting the role of magnetic symmetry in disk structure and accretion dynamics.

Findings

Even symmetric magnetic fields produce vertically thin disks.

Stronger magnetic fields reduce the accretion rate.

Hot magnetized flows can be fully advected in slim disks.

Abstract

We investigate the properties of a hot accretion flow bathed in a poloidal magnetic field. We consider an axisymmetric viscous resistive flow in the steady state configuration. We assume the dominant mechanism of energy dissipation is due to turbulence viscosity and magnetic diffusivity. A certain fraction of that energy can be advected towards the central compact object. We employ self-similar method in the radial direction to find a system of ODEs with just one varible, $\theta$ in the spherical coordinates. For the existence and maintaining of a purely poloidal magnetic in a rotating thick disk, we find the necessary condition is a constant value of angular velocity along a magnetic field line. We obtain an analytical solution for the poloidal magnetic flux. We explore possible changes in the vertical structure of the disk under the influences of even symmetric and asymmetric magnetic fields. Our results reveal that a polar magnetic field with even symmetry about the equatorial plane makes the disk vertically thin. Moreover, the accretion rate decreases when we consider a strong magnetic field. Finally, we notice hot magnetized accretion flows can be fully advected even in a slim shape.