Theory of Wind-Driving Protostellar Disks

Abstract

Observations reveal a strong link between disk accretion and energetic bipolar outflows in protostars. This connection could reflect the high efficiency of angular momentum transport by centrifugally driven winds launched from the disk surfaces along a large-scale, ordered magnetic field that threads the disk. Vertical angular momentum transport can also be achieved through torsional Alfvén waves that propagate along the magnetic field lines into the ambient medium. There is observational evidence for a dynamically significant “open” magnetic field in molecular cloud cores, and one can show that when a core collapses to form the central star and disk the magnetic field lines are advected inward by the inflowing gas. It is possible to construct semi-analytic equilibrium models of wind-driving disks with a realistic ionization and conductivity structure and investigate their stability properties. These studies are being complemented by non-ideal–MHD numerical simulations.