We perform a numerical study of the evolution of a Coronal Mass Ejection
(CME) and its interaction with the coronal magnetic field based on the May 12,
1997, CME event using a global MagnetoHydroDynamic (MHD) model for the solar
corona. The ambient solar wind steady-state solution is driven by photospheric
magnetic field data, while the solar eruption is obtained by superimposing an
unstable flux rope onto the steady-state solution. During the initial stage of
CME expansion, the core flux rope reconnects with the neighboring field, which
facilitates lateral expansion of the CME footprint in the low corona. The flux
rope field also reconnects with the oppositely orientated overlying magnetic
field in the manner of the breakout model. During this stage of the eruption,
the simulated CME rotates counter-clockwise to achieve an orientation that is
in agreement with the interplanetary flux rope observed at 1 AU. A significant
component of the CME that expands into interplanetary space comprises one of
the side lobes created mainly as a result of reconnection with the overlying
field. Within 3 hours, reconnection effectively modifies the CME connectivity
from the initial condition where both footpoints are rooted in the active
region to a situation where one footpoint is displaced into the quiet Sun, at a
significant distance ($\approx 1R_\odot$) from the original source region. The
expansion and rotation due to interaction with the overlying magnetic field
stops when the CME reaches the outer edge of the helmet streamer belt, where
the field is organized on a global scale. The simulation thus offers a new view
of the role reconnection plays in rotating a CME flux rope and transporting its
footpoints while preserving its core structure.
