A high-resolution study of the isotopes of solar flare nuclei

Abstract

Individual isotopes of the elements He, C, N, O, Ne, and Mg with energies from ~5 to ~50 MeV per nucleon have been resolved in energetic solar flare particles during the 1978 September 23 solar flare event. These C, N, and O measurements are the first solar flare isotope measurements reported for these elements. In addition, we have improved on our earlier determination of ^(22)Ne/^(20)Ne in this flare by extending the energy interval for isotope analysis. We continue to find a significant difference between the isotopic composition of solar flare and solar wind neon, which we compare to similar evidence from studies of solar energetic particles implanted in lunar and meteoritic samples. Although limited by statistics, our measurements of He, C, N, O, and Mg isotopes are consistent with typical isotopic abundances found in other samples of solar system material. The ensemble of these results is used to test for the possibility of mass-dependent fractionation during solar flare acceleration and propagation. Finally, measurements of the elemental composition and energy spectra of this event allow us to interpret our isotope measurements within a broader context of solar flare composition studies.

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