# Global Radiation-Magnetohydrodynamic Simulations of Black Hole Accretion Flow and Outflow: Unified Model of Three States - Astrophysics > High Energy Astrophysical Phenomena

Global Radiation-Magnetohydrodynamic Simulations of Black Hole Accretion Flow and Outflow: Unified Model of Three States - Astrophysics > High Energy Astrophysical Phenomena - Download this document for free, or read online. Document in PDF available to download.

Abstract: Black-hole accretion systems are known to possess several distinct modes orspectral states, such as low-hard state, high-soft state, and so on. Since thedynamics of the corresponding flows is distinct, theoretical models wereseparately discussed for each state. We here propose a unified model based onour new, global, two-dimensional radiation-magnetohydrodynamic simulations. Bycontrolling a density normalization we could for the first time reproduce threedistinct modes of accretion flow and outflow with one numerical code. When thedensity is large model A, a geometrically thick, very luminous disk forms, inwhich photon trapping takes place. When the density is moderate model B, theaccreting gas can effectively cool by emitting radiation, thus generating athin disk, i.e., the soft-state disk. When the density is too low for radiativecooling to be important model C, a disk becomes hot, thick, and faint; i.e.,the hard-state disk. The magnetic energy is amplified within the disk up toabout twice, 30%, and 20% of the gas energy in models A, B, and C,respectively. Notably, the disk outflows with helical magnetic fields, whichare driven either by radiation pressure force or magnetic pressure force, areubiquitous in any accretion modes. Finally, our simulations are consistent withthe phenomenological alpha-viscosity prescription, that is, the disk viscosityis proportional to the pressure.

Author: ** Ken Ohsuga, Shin Mineshige, Masao Mori, Yoshiaki Kato**

Source: https://arxiv.org/