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 nonspinning black hole. The disk has a thickness h/r similar to 0.05-0.1 over the radial range (2-20)GM/c(2).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 and Thorne. Also, the magnetic torque at the radius of the innermost stable circular orbit (ISCO) is only similar to 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.