Dissipative-Acoustic Instability in Accretion Disks at a Nonlinear Stage

Details Dissipative-Acoustic Instability in Accretion Disks at a Nonlinear Stage Dissipative-Acoustic Instability in Accretion Disks at a Nonlinear Stage

Apr 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003astl...29..246k&link_type=abstract

Astronomy Letters, vol. 29, p. 246-257 (2003)

Astronomy and Astrophysics

Astronomy

1

Scientific paper

Nonstationary hydrodynamic models of a viscous accretion disk around a central compact object were constructed. Two different numerical methods (TVD and SPH) are used to study the dynamics of dissipatively unstable acoustic perturbations at the nonlinear stage in terms of the standard alpha-disk model. The standard disk accretion in the Shakura-Sunyaev model is unstable against acoustic waves for various parameters of the system. If the alpha parameter, which specifies the level of turbulent viscosity, exceeds alpha > 0.03, then a complex nonstationary system of small-scale weak shock waves is formed. The growth rate of the perturbations is higher in the central disk region. For alpha > 0.2, the relative shock amplitude can exceed 50% of the equilibrium disk parameters. The reflection of waves from the disk boundaries and their nonlinear interaction are important factors that can produce unsteady accretion. The luminosity of such a disk undergoes quasi-periodic oscillations at a level of several percent (< 5%) of the equilibrium level.

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