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Angular momentum transport and thermal stabilization of optically thin, advective accretion flows through large-scale magnetic fields

Datta, SR and Mondal, T and Mukhopadhyay, B (2022) Angular momentum transport and thermal stabilization of optically thin, advective accretion flows through large-scale magnetic fields. In: Monthly Notices of the Royal Astronomical Society, 513 (1). pp. 204-222.

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Official URL: https://doi.org/10.1093/mnras/stac835


Outward transport of angular momentum, as well as viscous and thermal stability, are the necessary criteria for the formation of an accretion disc and to radiate steadily. Turbulent motions originating from magneto-rotational instability or hydrodynamic instability can do the required transport. We explore the effect of a large-scale magnetic field (LSMF) over the turbulent transport in an optically thin advective accretion disc. In this work, turbulent transport is represented through the usual Shakura-Sunyaev α-viscosity. The evolution of the magnetic field and other variables is found by solving vertically integrated height-averaged magnetohydrodynamic equations. Depending on its configuration, the LSMF can support or oppose α in outward transport of angular momentum. Once outward transport of angular momentum is assured, i.e. formation of the disc is confirmed through the combined effect of α-viscosity and the LSMF, we explore the impact of the LSMF in thermally stabilizing the disc. As found earlier, we also find that the advection of heat energy becomes zero or negative with an increasing accretion rate. That is why, at or above a critical accretion rate, the optically thin advective disc becomes thermally unstable. We show, however, that with the addition of a strong enough magnetic field, the disc regains its thermal stability and Joule heating turns out to play the key role in that. Throughout our analysis, the plasma-β (βm) remains within the range of 5-103, which does not impose any restriction in the simultaneous operation of the LSMF and the turbulent transport.

Item Type: Journal Article
Publication: Monthly Notices of the Royal Astronomical Society
Publisher: Oxford University Press
Additional Information: The copyright for this article belongs to the Authors.
Keywords: Angular momentum; Stability criteria; Thermodynamic stability; Viscosity, (magnetohydrodynamic) MHD; Accretion discs; Accretion rate; Accretion: accretion disks; Black Hole physics; Large-scales; Magnetic-field; Radiation mechanisms: nonthermal; Turbulent transports; X-rays: Binaries, Magnetohydrodynamics
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Date Deposited: 22 Sep 2022 09:56
Last Modified: 22 Sep 2022 09:56
URI: https://eprints.iisc.ac.in/id/eprint/76642

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