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Non-ideal magnetohydrodynamics (MHD) is the dominant process. We investigatethe effect of magnetic fields (ideal and non-ideal) and turbulence (sub- andtranssonic) on the formation of protostars by following the gravitationalcollapse of 1~M$_\odot$ gas clouds through the first hydrostatic core tostellar densities. The clouds are imposed with both rotational and turbulentvelocities, and are threaded with a magnetic field that isparallel/anti-parallel or perpendicular to the rotation axis; we investigatetwo rotation rates and four Mach numbers. The initial radius and mass of thestellar core are only weakly dependent on the initial parameters. In the modelsthat include ideal MHD, the magnetic field strength implanted in the protostarat birth is much higher than observed, independent of the initial level ofturbulence; only non-ideal MHD can reduce this strength to near or below theobserved levels. This suggests that not only is ideal MHD an incomplete pictureof star formation, but that the magnetic fields in low mass stars are implantedlater in life by a dynamo process. Non-ideal MHD suppresses magneticallylaunched stellar core outflows, but turbulence permits thermally launchedoutflows to form a few years after stellar core formation.

Non-ideal magnetohydrodynamics vs turbulence II: Which is the dominant process in stellar core formation?