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.