Other
Scientific paper
Jan 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009aas...21343704o&link_type=abstract
American Astronomical Society, AAS Meeting #213, #437.04; Bulletin of the American Astronomical Society, Vol. 41, p.309
Other
Scientific paper
We examine the evolution and influence of diskoseismic modes in simulated black hole accretion disks. Understanding the origin and behavior of such oscillations will help us to evaluate their potential role in producing astronomically observed high-frequency quasi-periodic oscillations in accreting black hole binary systems.
Our simulated disks are geometrically-thin with a constant half-thickness of five percent the radius of the innermost stable circular orbit. A pseudo-Newtonian potential is used to reproduce the relevant effects of general relativity. In one set of models, alpha-viscosity is included to provide angular momentum transport and the coupling of orthogonal velocity components in an otherwise ideal hydrodynamic numerical treatment of axisymmetric disks. Additionally, we conduct full three-dimensional magnetohydrodynamic disk simulations in which the magneto-rotational instability naturally drives turbulence and provides angular momentum transport.
We find that our simulated viscous disks characteristically develop and maintain trapped global mode oscillations with properties similar to those expected of trapped g-modes and inner p-modes in a narrow range of frequencies just below the maximum radial epicyclic frequency. Although the modes are driven in the inner portion of the disk, they generate waves that propagate at the trapped mode frequencies out to larger disk radii. This finding is contrasted with the results of global magnetohydrodynamic disk simulations, in which such oscillations are not easily identified. Such examples underscore fundamental physical differences between accretion systems driven by magnetic effects and those for which alpha-viscosity serves as a proxy for the physical processes that drive accretion.
Miller Michael Coleman
O'Neill Sean M.
Reynolds Chris S.
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