P.L. Slocum1, E.R. Christian2, C.M.S. Cohen3, A.C. Cummings3, R.A. Leske3, R.A. Mewaldt3, E.C. Stone3, T.T. von Rosenvinge2, and M.E. Wiedenbeck1 1 Jet Propulsion Laboratory, Pasadena, California USA 2 NASA/Goddard Space Flight Center, Greenbelt, Maryland USA 3 California Institute of Technology, Pasadena, California USA
Using the Solar Isotope Spectrometer (SIS) on the Advanced Composition Explorer (ACE), we have studied the properties of a selection of small solar energetic particle (SEP) events with heavy ion enhancements, relative to coronal values, in the energy range ~10-20 MeV/nucleon. These events contain significantly increased 3He/4He ratios over the solar wind value of 0.0004 in the energy range ~4.5-5.5 MeV/nucleon, and/or in the energy range ~0.1-10 MeV/nucleon as measured with the Ultra Low Energy Isotope Spectrometer (ULEIS) on ACE. Because SIS is not sensitive to 3He/4He ratios less than ~4% in the energy range ~4.5-5.5 MeV/nucleon due to spillover contamination from 4He, and the 3He abundance in each event decreases as a power law with energy, a subset of the events have measurable 3He enhancements at ULEIS but not at SIS energies. We will report on the nature of all of the events with respect to their heavy element content and other event characteristics, and will compare the results with those of previous studies. This research was supported by NASA at Caltech (under grant NAG5-6912), JPL, and GSFC.