Effects of Magnetic Field Loops on the Dynamics of Advective Accretion Flows and Jets around a Schwarzschild Blackhole

TL;DR

This paper investigates how magnetic field loops influence the dynamics of accretion flows and jet formation around a Schwarzschild black hole, revealing their role in shock oscillations and jet collimation.

Contribution

It presents a self-consistent study of flux tube dynamics within accretion flows, highlighting their impact on shock oscillations and jet acceleration mechanisms.

Findings

Magnetic flux tubes can be trapped inside the disc at high entropy regions.

Shock waves oscillate radially due to magnetic and centrifugal forces.

Toroidal magnetic fields contribute to jet collimation and acceleration.

Abstract

Magnetic fields advected along with low angular momentum accretion flows predominantly become toroidal due to the strong azimuthal velocity close to a black hole. We study self-consistently the movements of these flux tubes inside an advective disc and how they dynamically influence the flow. We find that the centrifugal barrier slows down the radial motion of the flux tubes. In this case, the large magnetic flux tubes with a significant drag force escape along the vertical axis due to buoyancy. Magnetic pressure rises close to the black hole and together with the centrifugal force, it combats gravity. The tug-of-war among these forces causes the centrifugal pressure supported shock to oscillate radially. We study the effects of successive injection of flux tubes and find how the flux tube could be trapped inside the disc in regions of highest entropy. Most interestingly, the shock wave remains at its average location and is not destroyed. We show that the toroidal field loops contribute significantly to collimate and accelerate the outflows from the centrifugal barrier and suggest this mechanism to be a way to collimate and accelerate jets.