Shearing box simulations of accretion disk winds^⋆

¹ Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Straße 1, 85748 Garching, Germany
² Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064, USA
e-mail: rainer@ucolick.org

Received: 11 October 2011
Accepted: 10 October 2012

Abstract

The launching process of a magnetically driven outflow from an accretion disk is investigated in a local shearing box model, which allows a study of the feedback between accretion and angular momentum loss. The mass-flux instability found in previous linear analyses of this problem is recovered in a series of 2D (axisymmetric) simulations in the MRI-stable (high magnetic field strength) regime. At low field strengths that are still sufficient to suppress MRI, the instability develops on a short radial length scale and saturates at a modest amplitude. At high field strengths, a long-wavelength “clump” instability of large amplitude and growth times of a few orbits is observed. As previously speculated, the unstable connection between disk and outflow may be relevant for the time dependence observed in jet-producing disks. The success of the simulations is due in large part to the implementation of an effective wave-transmitting upper boundary condition.