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Alpha-Viscosity Effects in Slender Tori

Journal article
Authors J. Horak
Marek A Abramowicz
Lina Levin
Rikard Slapak
O. Straub
Published in Publications of the Astronomical Society of Japan
Volume 64
Issue 4
ISSN 0004-6264
Publication year 2012
Published at Department of Physics (GU)
Language en
Keywords accretion disks, X-rays: binaries, accretion disks, oscillations, stability, modes
Subject categories Physical Sciences


We explore effects of the Shakura-Sunyaev alpha-viscosity on the dynamics and oscillations of slender tori. We start with a slow secular evolution of the torus. We show that the angular-momentum profile approaches the Keplerian one on a timescale longer than a dynamical one by a factor on the order of 1/alpha. We then focus our attention on the oscillations of the torus. We discuss the effects of various angular-momentum distributions. Using a perturbation theory, we have found a rather general result that the high-order acoustic modes are damped by the viscosity, while the high-order inertial modes are enhanced. We calculate viscous growth rates for the lowest-order modes, and show that already the lowest-order inertial mode is unstable for less-steep angular-momentum profiles, or very close to the central gravitating object.

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