  Star formation is thought to be triggered by the gravitational collapse of
the dense cores of molecular clouds. Angular momentum conservation during the
collapse results in the progressive increase of the centrifugal force, which
eventually halts the inflow of material and leads to the development of a
central mass surrounded by a disc. In the presence of an angular momentum
transport mechanism, mass accretion onto the central object proceeds through
this disc, and it is believed that this is how stars typically gain most of
their mass. However, the mechanisms responsible for this transport of angular
momentum are not well understood. The most promising are turbulence viscosity
driven by the magnetorotational instability (MRI), and outflows accelerated
centrifugally from the surfaces of the disc. Both processes are powered by the
action of magnetic fields and are, in turn, likely to strongly affect the
structure, dynamics, evolutionary path and planet-forming capabilities of their
host discs. The weak ionization of protostellar discs, however, may prevent the
magnetic field from effectively coupling to the gas and drive these processes.
Here I examine the viability and properties of these magnetically driven
processes in protostellar discs. The results indicate that, despite the weak
ionization, the field is able to couple to the gas and shear for fluid
conditions thought to be satisfied over a wide range of radii in these discs.
