J. E. Mazur The Aerospace Corporation G. M. Mason, J. R. Dwyer University of Maryland M. E. Wiedenbeck, P. L. Slocum Jet Propulsion Laboratory C. M. S. Cohen, A. C. Cummings, R. A. Leske, R. A. Mewaldt Caltech E. R. Christian, T. T. von Rosenvinge NASA/Goddard Space Flight Center R. E. Gold, S. M. Krimigis JHU/Applied Physics Laboratory
Since the launch of the Advanced Composition Explorer (ACE) in August 1997, numerous impulsive solar particle events have occurred, with a sharp increase beginning in early 1998 and continuing through at least the summer of 1999. Using the Ultra-Low-Energy Isotope Spectrometer (ULEIS) and Solar Isotope Spectrometer (SIS) on ACE, we have measured the energy spectra of 3He, 4He and heavy ions over the range ~0.1-10 MeV/nucleon in order to examine possible differences in the mechanisms responsible for the characteristic enhancements of 3He and heavy ions in these events. In some cases the 3He spectral form is significantly different from 4He, which may provide an important new clue to the acceleration process. We will compare the observed spectral forms with predictions from current theories for impulsive solar particle acceleration.