  We explore the pulsationally driven orbital mass ejection mechanism for Be
star disc formation using isothermal, 3D magnetohydrodynamic (MHD) and
hydrodynamic simulations. Non-radial pulsations are added to a star rotating at
95\% of critical as an inner boundary condition that feeds gas into the domain.
In MHD, the initial magnetic field within the star is weak. The hydrodynamics
simulation has limited angular momentum transport, resulting in repeating
cycles of mass accumulation into a rotationally-supported disc at small radii
followed by fall-back onto the star. The MHD simulation, conversely, has
efficient (Maxwell $\alpha_{\rm M}$ $\sim$ 0.04) angular momentum transport
provided by both of turbulent and coherent magnetic fields; a slowly decreting
midplane driven by the magnetorotational instability and a supersonic wind on
the surface of the disc driven by global magnetic torques. The angle and
time-averaged properties near the midplane agree reasonably well with a 1D
viscous decretion disc model with a modified $\tilde\alpha=0.5$, in which the
gas transitions from a subsonic thin disc to a supersonic spherical wind at the
critical point. 1D models, however, cannot capture the multi-phase
decretion/angular structure seen in our simulations. Our results demonstrate
that, at least under certain conditions, non-radial pulsations on the surface
of a rapidly rotating, weakly magnetized star can drive a Keplerian disc with
the basic properties of the viscous decretion disc paradigm, albeit coupled to
a laminar wind away from the midplane. Future modeling of Be star discs should
consider the possible existence of such a surface wind.
