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Colloquium
The Launch Mechanism of Protostellar Outflows

Abstract

The formation of protostellar disks and the generation of outflows resutls from a complex interaction of magnetic fields, gravity, and angular momentum. The nonideal MHD effects are also crucial to the outcome. Numerical calculations of this phenomenon are challenged by the need to achieve very high resolution near the central protostar, which then imposes strong time step restrictions. I review some recent three-dimensional nonideal MHD simulations that either resolve the central protostar, or use a central sink cell to evolve well into the Class 0 protostellar phase. In the latter case, we find new insights into the driving of the low-velocity outflow that emerges from near the disk edge. The launch region is identified as primarily the interface between the inwardly advected magnetic field of the pseudodisk and the outwardly diffusing magnetic field of the disk. I present some details of the structure and dynamics of the outflow zone.