Thermal Conduction in Clumpy Disks and BLR clouds

TL;DR

This paper explores how thermal conduction influences the dynamics and lifetime of clumpy structures within advection-dominated accretion flows, revealing that conduction accelerates cloud capture and reduces their lifespan.

Contribution

It introduces a detailed analysis of thermal conduction effects on clump dynamics in ADAFs, combining ensemble and individual cloud models with collision-less Boltzmann equation calculations.

Findings

Thermal conduction increases the radial velocity dispersion of clumps.

Conduction speeds up cloud capture via tidal forces.

Thermal conduction decreases the lifetime of clumpy structures.

Abstract

We investigate the dynamics of clumps that coexisted with/in advection-dominated accretion flows by considering thermal conductivity. Thermal conduction can be one of the effective factors in the energy transportation of ADAFs; hence it may indirectly affect the dynamics of clumps by means of a contact force between them and their host medium. We first study the ensemble of clumps by assuming them as collision-less particles and secondly we find the orbital motion of these clouds as individuals. For both parts, clumps are subject to the gravity of the central object and a drag force. The strong coupling between clumps and ADAF leads to equality between the average treatment of the clumps and the dynamics of their background. By employing the collision-less Boltzmann equation we calculate the velocity dispersion of the clumps which turns out approximately one order of magnitude higher than the ADAF. In fact, involving drag force in such a system causes the angular momentum of the clumps can be transported outwards by the ADAF, and hence the clouds eventually will be captured at the tidal radius. The results show that the presence of thermal conduction increases the root of the averaged radial velocity square and this in turn speeds up the process of capturing the clouds through the tidal force. In the end, we focus on a typical individual cloud, the spiral orbits appear thanks to only the toroidal component of friction force. The parametric study again proves that the operation of thermal conduction helps for decreasing the lifetime of clumps.