Solar Isotopic Composition as Determined Using Solar Energetic Particles |
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Authors: | R A Leske R A Mewaldt C M S Cohen A C Cummings E C Stone M E Wiedenbeck T T von Rosenvinge |
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Institution: | (1) Space Radiation Laboratory, California Institute of Technology, Pasadena, CA 91125, USA;(2) Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA;(3) NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA |
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Abstract: | 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. |
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Keywords: | Sun: abundances Sun: particle emission Sun: coronal mass ejections (CMEs) Sun: flares |
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