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Magnetic Fields in Accretion Disks*

Published online by Cambridge University Press:  05 March 2013

Marthijn de Kool ,
Geoffrey V. Bicknell  and
Zdenka Kuncic
Marthijn de Kool
Affiliation:
Astrophysical Theory Centre, Research School of Astronomy and Astrophysics, Private Bag, Weston Creek, ACT 2611, Australia
Geoffrey V. Bicknell
Affiliation:
Astrophysical Theory Centre, Research School of Astronomy and Astrophysics, Private Bag, Weston Creek, ACT 2611, Australia
Zdenka Kuncic
Affiliation:
Department of Physics and Astronomy, University of Victoria, Box 3055, Victoria, BC V8W 3P6, Canada
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Abstract

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This paper summarises our work on the role of magnetic fields in accretion disks presented in two papers elsewhere. In the first part (a summary of part of Kuncic & Bicknell 1999), we present a formal development of the equations governing the structure of an accretion disk containing magnetohydrodynamic turbulence. The importance of the different terms in the energy and momentum equations is discussed, and a parametrisation of the unresolved processes is suggested that could be used to make further progress. We briefly explore whether an MHD accretion disk can transport a significant part of the gravitational power into a corona by buoyancy. In the second part, we present some exploratory calculations of the vertical structure of accretion disks, in which non-local dissipation of energy due to the buoyant transport of magnetic field energy is taken into account. It is argued that the efficiency of buoyant magnetic transport depends very strongly on the size of the coherent magnetic regions. If the size of the buoyant cells is not very close to the disk thickness, magnetic energy generated by dynamo action inside the disk will be dissipated locally, and will not be available to transport a significant part of the accretion luminosity into a corona.

Keywords

accretion, accretion disksmagnetic fields
Type
Research Article
Information
Publications of the Astronomical Society of Australia , Volume 16 , Issue 3 , 1999 , pp. 225 - 233
Copyright
Copyright © Astronomical Society of Australia 1999

Footnotes

*

Refereed paper based on two separate contributions to the Workshop on Magnetic Fields and Accretion, held at the Astrophysical Theory Centre, Australian National University, on 12–13 November 1998.

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