  The most violent space weather events (eruptive solar flares and coronal mass
ejections) are driven by the release of free magnetic energy stored in the
solar corona. Energy can build up on timescales of hours to days, and then may
be suddenly released in the form of a magnetic eruption, which then propagates
through interplanetary space, possibly impacting the Earth's space environment.
Can we use the observed evolution of the magnetic and velocity fields in the
solar photosphere to model the evolution of the overlying solar coronal field,
including the storage and release of magnetic energy in such eruptions? The
objective of CGEM, the Coronal Global Evolutionary Model, funded by the
NASA/NSF Space Weather Modeling program, is to develop and evaluate such a
model for the evolution of the coronal magnetic field. The evolving coronal
magnetic field can then be used as a starting point for magnetohydrodynamic
(MHD) models of the corona, which can then be used to drive models of
heliospheric evolution and predictions of magnetic field and plasma density
conditions at 1AU.
