We numerically model the coronal mass ejection (CME) event of October 28,
2003 that erupted from active region 10486 and propagated to Earth in less than
20 hours causing severe geomagnetic storms. The magnetohydrodynamic (MHD) model
is formulated by first arriving at a steady state corona and solar wind
employing synoptic magnetograms. We initiate two CMEs from the same active
region, one approximately a day earlier that preconditions the solar wind for
the much faster CME on the 28th. This second CME travels through the corona at
a rate of over 2500 km s$^{-1}$ driving a strong forward shock. We clearly
identify this shock in an image produced by the Large Angle Spectrometric
Coronagraph (LASCO) C3, and reproduce the shock and its appearance in synthetic
white light images from the simulation. We find excellent agreement with both
the general morphology and the quantitative brightness of the model CME with
LASCO observations. These results demonstrate that the CME shape is largely
determined by its interaction with the ambient solar wind and may not be
sensitive to the initiation process. We then show how the CME would appear as
observed by wide-angle coronagraphs onboard the Solar Terrestrial Relations
Observatory (STEREO) spacecraft. We find complex time evolution of the
white-light images as a result of the way in which the density structures pass
through the Thomson sphere. The simulation is performed with the Space Weather
Modeling Framework (SWMF).
