This effort was supported under NASA contract NAS5-30302 at Lockheed Martin, by ISTP Program under UPN 370-17-43 at GSFC, and by NASA research grant NAG5-7721 at UCLA. We wish to thank N. A. Tsyanenko for making his latest version of the magnetic field model available to us for this study. W. K. P. thanks Dan Baker and the staff at LASP for their hospitality.