HEAD 2003 Meeting
Session 53. Active Galactic Nuclei II
Oral, Wednesday, March 26, 2003, 7:00-7:40pm

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[53.03] Radiatively Driven Instabilities in Accretion Flows

N. Turner, O. Blaes, S. Davis, A. Socrates (UCSB)

Radiative diffusion is often a significant source of damping of acoustic waves in astrophysical fluids. However, in a stratified medium with a background radiative flux, acoustic waves can be driven unstable by periodic radiative forcing. We believe this to be the basic physical mechanism behind a variety of instabilities that have been discussed in the literature, including hydrodynamic strange modes in stars and so-called ``photon bubble modes'' in radiation pressure supported accretion flows around black holes. We elucidate the basic physics of these instabilities, and also present simulations of their nonlinear evolution. Finally, we show how they may manifest themselves in observed spectral energy distributions and polarization. This work is supported by NSF grant AST-9970827 and a UCSB/Los Alamos CARE grant.

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Bulletin of the American Astronomical Society, 35#2
© 2003. The American Astronomical Soceity.