Simulations of Jet Production in Magnetized Accretion Disk Coronae

We describe the results of over 40 MHD simulations, performed on Caltech/JPL parallel supercomputers, of the coronae of magnetized accretion disks around compact objects. All produce some type of outflow from the disk. Our parameter study investigated the character of the outflow as a function of the strength of the initial poloidal magnetic field and its angle with respect to the disk rotation axis. When the radial component of the field is significant, this outflow takes the form of a collimated jet ejected from the center of the accretion disk. The jet velocity is a strong function of the strength of the initial magnetic field: for Alfv6n velocities (VA) below the escape speed (Vs.), the jet velocity is of order VA, but for VA only slightly above Vs., the jet velocity is an order of magnitude or more greater. This “magnetic switch” behaves similarly for a broad range of magnetic field polar angle. However, when the initial coronal magnetic field is nearly completely dominated by an axial component, the import ante of the central jet diminishes and the outflow becomes dominated by a poorly-collimated wind from a broader region of the accretion disk. The magnetic switch may have applications to galactic and extragalactic radio sources and other objects.