  An analytic model is developed for the erosion of protoplanetary gas discs by
high velocity magnetized stellar winds. The winds are centrifugally driven from
the surface of rapidly rotating, strongly magnetized young stars. The presence
of the magnetic field in the wind leads to Reynolds numbers sufficiently large
to cause a strongly turbulent wind/disk boundary layer which entrains and
carries away the disc gas. The model uses the conservation of mass and momentum
in the turbulent boundary layer. The time-scale for significant erosion depends
on the disc accretion speed and accretion rate and on the wind mass loss rate
and the wind velocity. The time-scale is estimated to be 2E6 yr. A significant
contribution to the disc erosion can come from frequent powerful coronal mass
ejections (CMEs) where the average mass loss rate in CMEs and velocities have
values comparable to those for the steady wind.
