Centrifugally driven winds from contracting molecular disks

Abstract

It is suggested that the bipolar outflows in dense molecular clouds that are associated with young stellar objects are steady and centrifugally driven hydromagnetic winds arising from the molecular disks in which the IR source is embedded. Acceleration to supersonic speeds is accomplished by the magnetic field embedded in the disk and extending outward beyond the wind region to join the galactic field. This analysis treats the problem of magnetic braking and energy transport in a partially ionized wind, and the basic parameter governing the flow is shown to be the ratio of the characteristic neutral ion collision time to flow time. A general analysis of angular momentum and energy transport is given, and the wind equation is solved along flux tubes in the strongly coupled limit. The centrifugally driven wind forms when an embedded protostar begins to ionize the disk core region. The disk core surface structure of the field is derived.