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

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 34S, 38Ar, 44Ca, 54Fe, and 60Ni, 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 22Ne/20Ne and 26Mg/24Mg. Overall, the enrichments of the isotope ratios show a correlation with the ratio of masses, M2/M1, scaling approximately as (M2/M1)7, although significant deviations from this trend are evident.

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