Bipolar molecular outflows driven by hydromagnetic protostellar winds

We demonstrate that magnetically collimated protostellar winds will sweep a mbient material into thin, radiative, momentum-conserving shells whose feat ures reproduce those commonly observed in bipolar molecular outflows. We fi nd that the typical position-velocity and mass-velocity relations occur in outflows in a wide variety of ambient density distributions, regardless of the time histories of their driving winds.