The origin of molecular protostellar outflows

We study the geometry of the large scale magnetic field threading the centr ifugally supported circumstellar disk that forms in the inner few hundred A U of a dynamically collapsing protostellar molecular cloud core. The disk i s highly turbulent, therefore highly diffusive, thus unable by itself to su fficiently stretch and bend the large scale magnetic field so as to launch magnetically driven winds from its surface. However, when we take proper ac count of the fact that the magnetic field is already highly stretched and b ent in the outside dynamically collapsing cloud core, we discover that this contributes to significant outward magnetic field bending around the outer edge of the inner protoplanetary disk too. We obtain the field geometry se lf-consistently under general simplifying approximations. We also show how this magnetic field geometry leads naturally to strong magneto-centrifugall y driven outflows from the surface of the disk, with mass loss rates a sign ificant fraction of the accretion rate onto the inner disk. Our simple pict ure describes naturally the origin of the molecular winds observed during t he end stages of protostellar cloud collapse.