Dynamics of Magnetic Flux Tubes in an Advective Flow around a Black Hole

TL;DR

This paper investigates how magnetic flux tubes behave within advective accretion flows around black holes, revealing their potential role in jet collimation and acceleration through numerical simulations.

Contribution

It introduces a study of flux tube trajectories in thick accretion flows with shocks, highlighting their influence on outflow properties and jet formation.

Findings

Flux tubes can move inward or oscillate before escaping.

Flux tubes significantly affect outflow collimation and acceleration.

Magnetic flux tubes may play a pivotal role in jet dynamics.

Abstract

Entangled magnetic fields entering into an accretion flow would very soon be stretched into a dominant toroidal component due to strong differentially rotating motion inside the accretion disc. This is particularly true for weakly viscous, low angular momentum transonic or advective discs. We study the trajectories of toroidal flux tubes inside a geometrically thick flow which undergoes a centrifugal force supported shock. We also study effects of these flux tubes on the dynamics of the inflow and the outflow. We use a finite difference method (Total Variation Diminishing) for this purpose and specifically focussed on whether these flux tubes significantly affect the properties of the outflows such as its collimation and the rate. It is seen that depending upon the cross-sectional radius of the flux tubes which control the drag force, these field lines may move towards the central object or oscillate vertically before eventually escaping out of the funnel wall (pressure zero surfaces) along the vertical direction. A comparison of results obtained with and without flux tubes show these flux tubes could play pivotal role in collimation and acceleration of jets and outflows.