FORMATION OF STATIONARY MAGNETOHYDRODYNAMIC OUTFLOWS FROM A DISK BY TIME-DEPENDENT SIMULATIONS

We report the discovery of a family of stationary magnetohydrodynamic (MHD) outflows from a disk found by time-dependent, axisymmetric MHD s imulations. The initial poloidal magnetic field threading the disk was taken to be a tapered monopole field, with the field strength on the disk decreasing outwardly to small values. At the disk surface, matter was given a small initial push with a speed less than the slow magnet osonic speed. In the simulations, the outflowing matter is observed to be accelerated by magnetic and centrifugal forces up to velocities in excess of the fast magnetosonic speed and in excess of the escape spe ed.