  On October 28, 2003 an earthward-directed coronal mass ejection (CME) was
observed from SOHO/LASCO imagery in conjunction with an X17 solar flare. The
CME, traveling at nearly 2000 km/s, impacted the Earth on October 29, 2003
causing ground-based particle detectors to register a counting rate drop known
as a Forbush decrease. In addition to affecting the rate of cosmic rays, the
CME was also responsible for causing anisotropies in the direction of
incidence. Data from Project GRAND, an array of proportional wire chambers, are
presented during the time of this Forbush decrease. A simple model for CME
propagation is proposed and we present an argument based on gyroradius that
shows that a magnetic field of the radius calculated for the ejecta is
sufficient to deflect energetic charged particles of an energy detectable by
GRAND.
