  The majority of stars are thought to form in clusters. Cluster formation in
dense clumps of molecular clouds is strongly influenced, perhaps controlled, by
supersonic turbulence. We have previously shown that the turbulence in regions
of active cluster formation is quickly transformed by the forming stars through
protostellar outflows, and that the outflow-driven protostellar turbulence is
the environment in which most of the cluster members form. Here, we take
initial steps in quantifying the global properties of the protostellar
turbulence through 3D MHD simulations. We find that collimated outflows are
more efficient in driving turbulence than spherical outflows that carry the
same amounts of momentum. Gravity plays an important role in shaping the
turbulence, generating infall motions in the cluster forming region that
balance the outward motions driven by outflows. The resulting quasi-equilibrium
state is maintained through a slow rate of star formation, with a fraction of
the total mass converted into stars per free fall time as low as a few percent.
Magnetic fields are dynamically important even in magnetically supercritical
clumps, provided that their initial strengths are not far below the critical
value for static cloud support. We find that the mass weighted PDF of the
volume density is often, although not always, approximately lognormal. The PDFs
of the column density deviate more strongly from lognormal distributions. There
is a prominent break in the velocity power spectrum of the protostellar
turbulence, which may provide a way to distinguish it from other types of
turbulence.
