Unusual isotopic composition of solar energetic particles observed in the November 6, 1997 event

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

Abstract

Using the Solar Isotope Spectrometer on the Advanced Composition Explorer, we have measured the isotopic composition of solar energetic particles (SEPs) with energies of tens of MeV/nucleon during the November 6, 1997 solar event, including isotopes never before reported in SEPs, such as ^(34)S, ^(38)Ar, ^(44)Ca, ^(54)Fe, and ^(60)Ni, as well as isotopes of C, N, O, Ne, Mg, and Si. Abundances are found to be enhanced by factors of ∼2 relative to the standard solar system values for ^(22)Ne/^(20)Ne and ^(26)Mg/^(24)Mg. Overall, the enrichments of the isotope ratios show a correlation with the ratio of masses, M_2/M_1, scaling approximately as (M_2/M_1)^7, although significant deviations from this trend are evident.

Additional Information

© 1998 by the American Geophysical Union. Received September 9, 1998; accepted October 2, 1998. Paper number 1998GL900173. 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. We are grateful to the large group of dedicated and talented individuals who made the ACE mission possible and contributed to the development of the SIS instrument (as acknowledged in Stone et al., (1998]).

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