Other
Scientific paper
May 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agusmsh43c..06w&link_type=abstract
American Geophysical Union, Spring Meeting 2008, abstract #SH43C-06
Other
2114 Energetic Particles (7514), 7514 Energetic Particles (2114)
Scientific paper
In 3He-rich solar energetic particle (SEP) events, the 3He/4He ratio is often enhanced by 2 to 4 orders of magnitude over the solar wind value, while heavy element composition in these events is characterized by abundance enhancements that typically increase with increasing atomic number, Z. The ratio Fe/O, which is commonly used as a measure of the degree of heavy element fractionation in these events, can often exceed the coronal photospheric value by a factor of 10 or more. Recently measurements of elements heavier than Fe ("ultraheavy elements") have shown that the trend of increasing abundance enhancements with increasing Z extends to the top of the periodic table. The isotopic composition of individual elements can provide another diagnostic of the physical process(es) responsible for fractionation in 3He-rich SEP events and has the advantage that the relative mass-to-charge ratio of different isotopes of the same element is a known quantity (assuming acceleration from the same thermal population). A survey has been made of the isotopic composition of the elements Ne and Mg in 26 3He-rich SEP events measured using the Solar Isotope Spectrometer on the NASA Advanced Composition Explorer (ACE). These events, which occurred between September 1998 and November 2004, had relatively high intensities and hard energy spectra when compared with typical 3He-rich events and thus allowed isotope measurements above ~10 MeV/nuc. We will report the isotopic composition measurements and discuss correlations with elemental abundances measured in the same events. We will also compare these high energy isotope measurements with results obtained at lower energies (Dwyer et al., ApJ, 563, 403, 2001). This work was supported by NASA at Caltech (under grant NAG5-12929), JPL, and GSFC.
Cohen Charon
Cummings Alan C.
Leske Richard A.
Mewaldt Richard A.
Stone Edward C.
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