HR: 17:30h
AN: SH14A-07    [Abstracts]
TI: Measurements of Ultra-Heavy Elements in Solar Energetic Particle Events Above 10 MeV/nucleon
AU: * Leske, R A
EM: ral@srl.caltech.edu
AF: California Institute of Technology, Mail Code 220-47, Pasadena, CA 91125 United States
AU: Cohen, C M
SH14A-07 AF: California Institute of Technology, Mail Code 220-47, Pasadena, CA 91125 United States
AU: Cummings, A C
SH14A-07 AF: California Institute of Technology, Mail Code 220-47, Pasadena, CA 91125 United States
AU: Mewaldt, R A
SH14A-07 AF: California Institute of Technology, Mail Code 220-47, Pasadena, CA 91125 United States
AU: Stone, E C
SH14A-07 AF: California Institute of Technology, Mail Code 220-47, Pasadena, CA 91125 United States
AU: Wiedenbeck, M E
SH14A-07 AF: Jet Propulsion Laboratory, MS 169-327, Pasadena, CA 91109 United States
AU: von Rosenvinge, T T
SH14A-07 AF: NASA/Goddard Space Flight Center, Code 661, Greenbelt, MD 20771 United States
AB: Recent measurements from Wind/LEMT and ACE/ULEIS show that abundances of elements heavier than Ni (Z=28) can be enhanced relative to oxygen by factors of ~100 to 1000 (depending on species) in impulsive solar energetic particle (SEP) events at energies below several MeV/nucleon. The Solar Isotope Spectrometer (SIS) on ACE measures the composition of energetic nuclei for elements up to ~Zr (Z=40) at energies from ~10 to >100 MeV/nucleon. At these energies, even large gradual events often are very iron rich and may appear similar in composition to impulsive events, perhaps due to admixtures of flare seed material. Since August 1997, SIS has recorded ~1000 nuclei with Z≥29, including measurable quantities of Zn, Ge and Se (Z=30, 32, and 34). We present observations that establish the potential of extending ultra-heavy SEP measurements up to higher energies in order to test models of acceleration and abundance enhancements in both gradual and impulsive events. We find that the long-term average composition for elements from Z=30 to 40 appears to be similar to standard solar system values above 10 MeV/nucleon, but that there is considerable event-to-event variability. In particular, the event of 23 July 2004 is found to have very large enhancements in ultra-heavy ions at energies >10 MeV/nucleon, with a (34<Z<40)/O enhancement of ~250-300 times the standard solar value. This work was supported by NASA at Caltech (under grant NAG5-6912), JPL, and GSFC.
DE: 2114 Energetic particles (7514)
DE: 7513 Coronal mass ejections (2101)
DE: 7514 Energetic particles (2114)
SC: SPA-Solar and Heliospheric Physics [SH]
MN: Fall Meeting 2005