Thermal Conduction and Thermal-Driven Winds in Magnetized Viscous Accretion Disk Dynamics

TL;DR

This study models how thermal conduction and winds affect magnetized accretion disks around rotating black holes, revealing their impact on shock formation, disk dynamics, and outburst evolution.

Contribution

It introduces a self-consistent steady model incorporating thermal conduction and winds in magnetized accretion flows onto rotating black holes, analyzing their effects on shock behavior and outburst characteristics.

Findings

Steady, transonic, shocked accretion solutions are found around rotating black holes.

Shock location moves outward with increasing thermal conduction and wind parameters.

The model explains the decreasing QPO frequency during black hole outburst decay.

Abstract

This paper investigates the effects of saturated thermal conduction (TC) and thermal-driven winds (TDWs) on magnetized advection-dominated accretion onto a rotating black hole (BH). We incorporate dissipative processes in the magnetized accretion flow and expect the accretion disk to be threaded by predominantly toroidal and turbulent magnetic fields. We solve the magnetohydrodynamics equations and construct a self-consistent steady model of the magnetized accretion flow surrounding a rotating BH, which includes TC and TDWs. We seek global accretion solutions spanning from the BH horizon to a large distance and analyze the solution's characteristics as a function of dissipation parameters. Accretion solutions with multiple critical points may exhibit shock waves if they meet the standing shock criteria. We found steady, global transonic, and shocked accretion solutions around the rotating BH. In particular, the wind parameter ($m$) and the saturated conduction parameter ($\Phi_{\rm s}$) significantly influence the dynamical behavior of shocks. The shock location moves away from the BH horizon as $\Phi_{\rm s}$ and $m$ increase, assuming fixed conditions at the disk's outer edge. Our formalism explains the declining phase of BH outbursts, characterized by a monotonic decrease in QPO frequency as the burst decays. Based on our findings, we conclude that the combined effect of $\Phi_{\rm s}$ and $m$ parameters substantially alters the steady shock specific energy vs angular momentum parameter space and also modifies the corresponding post-shock luminosity vs QPO frequency parameter space. We propose, based on our theoretical model, that the $\Phi_{\rm s}$ and $m$ parameters may significantly influence the evolution of the BH outbursts.