A magnetic scaleheight: the effect of toroidal magnetic fields on the thickness of accretion discs |
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Authors: | Kurt Liffman Anne Bardou |
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Institution: | Advanced Fluid Dynamics Lab, CSIRO/BCE, PO Box 56, Highett, Victoria 3190, Australia; Department of Mathematics, University of Newcastle, Newcastle Upon Tyne NE1 7RU |
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Abstract: | We consider accreting systems in which the central object interacts, via the agency of its magnetic field, with the disc that surrounds it. The disc is turbulent and, so, has a finite effective conductivity. The field sweeps across the face of the disc, thereby forming a current that is directed radially within the disc. In turn, this disc current creates a toroidal field, where the interaction between the disc current and the toroidal field produces a Lorentz force that compresses the disc. We investigate this compression, which creates a magnetic scaleheight of the disc that can be much smaller than the conventional scaleheight. We derive an analytic expression for the magnetic scaleheight and apply it to fully ionized discs. |
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Keywords: | accretion accretion discs magnetic fields MHD stars: magnetic fields |
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