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Event Detail Information

Event Detail Information

Speaker Yan-Fei Jiang (Harvard University)
Date Oct 9, 2013
Time 12:00 pm  
Location 464 Loomis
Sponsor Department of Physics
Phone 3124045023
Event type Seminar
Views 3215
Structures and thermal properties of the black hole accretion disks in the radiation pressure dominated regime will be discussed. Angular momentum transfer in the disk is provided by the turbulence generated by the magneto-rotational instability (MRI), which is calculated self-consistently with a recently developed 3D radiation magneto-hydrodynamics (MHD) code based on Athena. The thermal instability of the radiation pressure dominated disks is studied with vertically stratified shearing box simulations. I always find that the radiation pressure dominated disks either collapse or expand until we have to stop the simulations. During the thermal runaway, the heating and cooling rates from the simulations are consistent with the general criterion of thermal instability. However, details of the thermal runaway are different from the predictions of the standard alpha disk model. We also identify the key reasons why previous simulations do not find the instability. A new mechanism to generate high temperature corona above the accretion disk is also found from these simulations. The thermal instability has many important implications for understanding the observations of both X-ray binaries and Active Galactic Nuclei.