Numerical Simulations of Astrophysical Jets from Keplerian Disks. I. Stationary Models

Abstract

We present 2.5-dimensional time-dependent simulations of the evolution of nonrelativistic outows from Keplerian accretion disks orbiting low-mass protostars or black holes accreting at sub-Eddington rates. The gas is injected at a very small speed from the surface of the disk (a xed (v inj \ 10~3v K ) boundary in our simulations) into a cold corona. The corona is in stable equilibrium and is supported by Alfve nic turbulent pressure. The initial magnetic eld conguration in the corona is poloidal and is given by a potential eld (J \ 0). This conguration is extended smoothly into the disk where the toroidal magnetic eld is taken to scale inversely with the disk radius. We present the analytical and the numerical approaches to our problem, as well as many results for a steady state simulation. We nd that the gas is centrifugally accelerated through the Alfve n and the fast magnetosonic (FM) surfaces and collimated into cylinders parallel to the disks axis. The collimation of the outow is due to the pinch force exerted by the dominant toroidal magnetic eld generated by the outow itself. Beyond the FM surface, we found that a "" Hubble ow is present ;