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Published June 2007 | public
Journal Article

Solar Isotopic Composition as Determined Using Solar Energetic Particles


Solar energetic particles (SEPs) provide a sample of the Sun from which solar composition may be determined. Using high-resolution measurements from the Solar Isotope Spectrometer (SIS) onboard NASA's Advanced Composition Explorer (ACE) spacecraft, we have studied the isotopic composition of SEPs at energies ≥20 MeV/nucleon in large SEP events. We present SEP isotope measurements of C, O, Ne, Mg, Si, S, Ar, Ca, Fe, and Ni made in 49 large events from late 1997 to the present. The isotopic composition is highly variable from one SEP event to another due to variations in seed particle composition or due to mass fractionation that occurs during the acceleration and/or transport of these particles. We show that various isotopic and elemental enhancements are correlated with each other, discuss the empirical corrections used to account for the compositional variability, and obtain estimated solar isotopic abundances. We compare the solar values and their uncertainties inferred from SEPs with solar wind and other solar system abundances and find generally good agreement.

Additional Information

© Springer Science + Business Media, Inc. 2007. Received: 2 February 2007. Accepted: 3 April 2007. Published online: 25 May 2007. This work was supported by NASA at the California Institute of Technology (grant NAG5-12929), the Jet Propulsion Laboratory, and the Goddard Space Flight Center.

Additional details

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October 20, 2023