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The Stability of a Warped Accretion Disc

Published online by Cambridge University Press:  25 April 2016

Colin S. Coleman
Affiliation:
Department of Mathematics, Monash University, Melbourne Vic 3168
Sanjiv Kumar
Affiliation:
Department of Theoretical Physics, Oxford University, UK

Abstract

An accretion disc becomes warped when subjected to a torque which is misaligned with the disc plane. Such torques may be caused by Lense-Thirring precession near a spinning compact object, or the quadrupole field of a binary star. Here the flow in an adiabatic warped disc is modelled as a two-dimensional shear layer with linear velocity profile and free surface boundary conditions, and is investigated by means of a linear stability analysis.

The flow is found to be unstable whenever it contains a critical layer, i.e., a level at which the shear velocity is equal to the phase velocity. The instability occurs over a broad wavenumber range and has a typical dimensionless growth rate ≈ 0.1 for both the compressible and incompressible cases. These waves grow with a time-scale of about one orbital period, and are likely to have a major effect on the disc viscosity.

Type
Extragalactic
Copyright
Copyright © Astronomical Society of Australia 1991

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