Three-dimensional Simulations of Magnetized Thin Accretion Disks around Black Holes: Stress in the Plunging Region

We describe three-dimensional general relativistic magnetohydrodynamic simulations of a geometrically thin accretion disk around a non-spinning black hole. The disk has a thickness h/r ∼ 0.05−0.1 over the radius range (2−20)GM/c2. In steady state, the specific angular momentum profile of the inflowing magnetized gas deviates by less than 2% from that of the standard thin disk model of Novikov & Thorne (1973). In addition, although the magnetic torque at the radius of the innermost stable circular orbit (ISCO) does not vanish, it is only ∼ 2% of the inward flux of angular momentum at this radius. Both results indicate that magnetic coupling across the ISCO is relatively unimportant for geometrically thin disks around non-spinning black holes. Subject headings: X-ray: stars — binaries: close — accretion, accretion disks — black hole physics