In parallel with these developments, MHD simulations have advanced our understanding of the nature of viscosity in accretion disks. The magnetorotational instability (MRI) has been shown to be a source of turbulent viscosity (Balbus & Hawley 1991), a result that has been confirmed by several global GR MHD simulations (e.g., DeVilliers et al. 2003; McKinney & Gammie 2004; Matsumoto et al. 2004). Investigators are now considering how MRI and MHD turbulence influences disk structure (e.g., Gammie 2004), the emerging thermal spectrum (e.g., Merloni 2003), and Comptonization effects (e.g., Socrates et al. 2004). MHD simulations of accretion disks are currently three-dimensional, global and based on the Kerr metric. They will soon include dissipative processes (i.e., radiation; see Johnson & Gammie 2003), and it is hoped that they will then connect more directly with observation.
Source: Remillard & McClintock 2006 ┃ X-Ray Properties… ⚬𓂃
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