  Rotating outflows from protostellar disks might trace extended
magneto-hydrodynamic (MHD) disk winds (DWs), providing a solution to the
angular momentum problem in disk accretion for star formation. In the jet
system HH 212, a rotating outflow was detected in SO around an episodic jet
detected in SiO. Here we spatially resolve this SO outflow into three
components: a collimated jet aligned with the SiO jet, the wide-angle disk
outflow, and an evacuated cavity in between created by a large jet-driven
bowshock. Although it was theoretically predicted before, it is the first time
that such a jet-DW interaction is directly observed and resolved, and it is
crucial for the proper interpretation and modeling of non-resolved DW
candidates. The resolved kinematics and brightness distribution both support
the wide-angle outflow to be an extended MHD DW dominating the local angular
momentum extraction out to 40 au, but with an inner launching radius truncated
to $\gtrsim 4$ au. Inside 4 au, where the DW may not exist, the
magneto-rotational instability (MRI) might be transporting angular momentum
outwards. The jet-DW interaction in HH 212, potentially present in other
similar systems, opens an entirely new avenue to probe the large-scale magnetic
field in protostellar disks.
