  Magnetic fields are observed in star forming regions. However simulations of
the late stages of star formation that do not include magnetic fields provide a
good fit to the properties of young stars including the initial mass function
(IMF) and the multiplicity. We argue here that the simulations that do include
magnetic fields are unable to capture the correct physics, in particular the
high value of the magnetic Prandtl number, and the low value of the magnetic
diffusivity. The artificially high (numerical and uncontrolled) magnetic
diffusivity leads to a large magnetic flux pervading the star forming region.
We argue further that in reality the dynamics of high magnetic Prandtl number
turbulence may lead to local regions of magnetic energy dissipation through
reconnection, meaning that the regions of molecular clouds which are forming
stars might be essentially free of magnetic fields. Thus the simulations that
ignore magnetic fields on the scales on which the properties of stellar masses,
stellar multiplicities and planet-forming discs are determined, may be closer
to reality than those which include magnetic fields, but can only do so in an
unrealistic parameter regime.
