Thin accretion disc with a corona in a central magnetic field

TL;DR

This paper presents an analytical model of a magnetized accretion disc with a corona around a rotating star, showing how magnetic interactions and corona presence influence disc structure and properties.

Contribution

It introduces a fully analytical solution for the disc-corona system considering magnetic interactions and energy transfer, highlighting the impact on disc density and temperature.

Findings

Corona increases surface density of the disc.

Corona reduces the disc temperature.

Strong magnetic fields and rapid stellar rotation significantly alter disc profiles.

Abstract

We study the steady-state structure of an accretion disc with a corona surrounding a central, rotating, magnetized star. We assume that the magneto-rotational instability is the dominant mechanism of angular momentum transport inside the disc and is responsible for producing magnetic tubes above the disc. In our model, a fraction of the dissipated energy inside the disc is transported to the corona via these magnetic tubes. This energy exchange from the disc to the corona which depends on the disc physical properties is modified because of the magnetic interaction between the stellar magnetic field and the accretion disc. According to our fully analytical solutions for such a system, the existence of a corona not only increases the surface density but reduces the temperature of the accretion disc. Also, the presence of a corona enhances the ratio of gas pressure to the total pressure. Our solutions show that when the strength of the magnetic field of the central neutron star is large or the star is rotating fast enough, profiles of the physical variables of the disc significantly modify due to the existence of a corona.