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N. J. Turner, J. M. Stone (Astronomy Dept, Univ of Maryland), J. H. Krolik (Physics & Astronomy Dept, Johns Hopkins Univ), T. Sano (Astronomy Dept, Univ of Maryland)
In the central regions of the accretion disks around compact objects in active galactic nuclei and X-ray binary stars, radiation pressure may exceed gas pressure. We describe results of 3-D numerical MHD simulations of local patches of such a disk. Vertical stratification is neglected, and the radiation is treated using a diffusion approximation. Magneto-rotational instability leads to the development of sustained turbulence, in which angular momentum is transported outwards primarily by magnetic stresses. We investigate the dependence of the saturation amplitude on the ratio of radiation to gas pressure. Diffusion of radiation from compressed regions converts kinetic energy into radiation energy, and results in density fluctuations larger than in the corresponding gas pressure dominated calculation. Implications for observed disks are discussed.