  The Accretion-Ejection Instability (AEI) is explored numerically using a
global 2d model of the inner region of a magnetised accretion disk. The disk is
initially currentless but threaded by an external vertical magnetic field
created by external currents, and frozen in the flow. In agreement with the
theory a spiral instability, similar in many ways to those observed in
self-gravitating disks, but driven by magnetic stresses, develops when the
magnetic field is close to equipartition with the disk thermal pressure. The
present non-linear simulations give good evidence that such an instability can
occur in the inner region of accretion disks.
