Measurements of the Heavy-Ion Isotopic Composition of Solar Energetic Particles

Creators: Leske, R. A.; Mewaldt, R. A.; Cohen, C. M. S.; Cummings, A. C.; Slocum, P. L.; Stone, E. C.; von Rosenvinge, T. T.; Wiedenbeck, M. E.

Others:: Kieda, D.; Salamon, M.; Dingus, B.

Abstract

Using the Solar Isotope Spectrometer (SIS) on the Advanced Composition Explorer (ACE) spacecraft, we have measured the isotopic composition of ten elements from C to Ni (Z = 6 to 28) at energies of tens of MeV/nucleon in as many as nine solar energetic particle (SEP) events that have occurred since November 1997. We find that the isotopic composition varies dramatically from event to event. For example, the ^(22)Ne/^(20)Ne ratio ranges from ~0.7 to 2 times the solar wind value. The mass fractionation is strongly correlated with the Fe/O and other element abundance ratios, suggesting that the elemental and isotopic fractionation are governed by the same process.

Additional Information

© University of Utah. Provided by the NASA Astrophysics Data System This research was supported by NASA at the California Institute of Technology (under grant NAG5-6912), the Jet Propulsion Laboratory, and the Goddard Space Flight Center.

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