  We present the results of a numerical magnetohydrodynamic simulation that
demonstrates a mechanism by which magnetic fields tap rotational energy of a
stellar core and expel the envelope. Our numerical setup, designed to focus on
the basic physics of the outflow mechanism, consists of a solid, gravitating
sphere, which may represent the compact core of a star, surrounded by an
initially hydrostatic envelope of ionized gas. The core is threaded by a
dipolar magnetic field that also permeates the envelope. At the start of the
simulation, the core begins to rotate at 10% of the escape speed. The magnetic
field is sufficiently strong to drive a magneto-rotational explosion, whereby
the entire envelope is expelled, confirming the expectation of analytical
models. Furthermore, the dipolar nature of the field results in an explosion
that is enhanced simultaneously along the rotation axis (a jet) and along the
magnetic equator. While the initial condition is simplified, the simulation
approximates circumstances that may arise in astrophysical objects such as Type
II supernovae, gamma ray bursts, and proto-planetary nebulae.
