Magnetically controlled accretion onto a black hole

TL;DR

This paper explores a magnetically controlled accretion model onto black holes where magnetic fields significantly alter the accretion flow, preventing disk formation and potentially leading to jet and radiation production.

Contribution

It introduces the Magnetically Controlled Accretion (MCA) scenario, highlighting how magnetic fields influence accretion dynamics and energy conversion near black holes.

Findings

Magnetic fields prevent the formation of a Keplerian disk.

Accretion occurs via a magnetized slab rather than a disk.

Magnetic instabilities may produce jets and high-energy radiation.

Abstract

An accretion scenario in which the material captured by a black hole from its environment is assumed to be magnetized (\beta ~ 1) is discussed. We show that the accretion picture in this case is strongly affected by the magnetic field of the flow itself. The accretion power within this Magnetically Controlled Accretion (MCA) scenario is converted predominantly into the magnetic energy of the accretion flow. The rapidly amplified field prevents the accretion flow from forming a homogeneous Keplerian disk. Instead, the flow is decelerated by its own magnetic field at a large distance (Shvartsman radius) from the black hole and switches into a non-Keplerian dense magnetized slab. The material in the slab is confined by the magnetic field and moves towards the black hole on the time scale of the magnetic field annihilation. The basic parameters of the slab are evaluated. Interchange instabilities in the slab may lead to a formation of Z-pinch type configuration of the magnetic field over the slab in which the accretion power can be converted into jets and high-energy radiation.