HR: 0800h
AN: SH11B-0267    [Abstracts]
TI: Heavy-ion Composition of Solar Energetic Particles Observed During 3He-rich Periods
AU: * Wiedenbeck, M E
EM: mark.e.wiedenbeck@jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology, MS 169-327 4800 Oak Grove Dr., Pasadena, CA 91109 United States
AU: Cohen, C M
SH11B-0267 AF: California Institute of Technology, MS 220-47, Pasadena, CA 91125 United States
AU: Cummings, A C
SH11B-0267 AF: California Institute of Technology, MS 220-47, Pasadena, CA 91125 United States
AU: Leske, R A
SH11B-0267 AF: California Institute of Technology, MS 220-47, Pasadena, CA 91125 United States
AU: Mewaldt, R A
SH11B-0267 AF: California Institute of Technology, MS 220-47, Pasadena, CA 91125 United States
AU: Stone, E C
SH11B-0267 AF: California Institute of Technology, MS 220-47, Pasadena, CA 91125 United States
AU: von Rosenvinge, T
SH11B-0267 AF: NASA/Goddard Space Flight Center, Code 661, Greenbelt, MD 20771 United States
AB: Impulsive solar energetic particle (SEP) events are characterized by large excesses of ³He/⁴He relative to the solar wind value of 0.0005 and a pattern of increasing heavy element abundance enhancement factors with increasing atomic number, Z, or mass, M. Because the heavy-ion energy spectra observed in these events are generally soft, relatively little is known about their elemental and isotopic composition above several MeV/nucleon. However, a few relatively-large ³He-rich SEP events in August 2002 provided statistically-significant samples of nuclei up through Z=30 above 10 MeV/nuc as well as isotopic composition data for several major elements. Heavy element abundances in these event were highly fractionated and not well-ordered by Z or M. In order to investigate how common this sort of fractionation is in impulsive events we have surveyed 8+ years of data from the Solar Isotope Spectrometer on ACE using two different approaches. First, heavy ion abundances were derived for those ³He-rich events in which statistically-significant measurements were possible. And second, data were combined from a large number of ³He-rich time periods in order derive the fluence-weighted composition in such periods. We present and compare composition results obtained using these two approaches and discuss their implications for the origin of impulsive SEP events. This work was supported by NASA at Caltech (under grant NAG5-6912), JPL, and GSFC.
DE: 2114 Energetic particles (7514)
DE: 7514 Energetic particles (2114)
SC: SPA-Solar and Heliospheric Physics [SH]
MN: Fall Meeting 2005