Nickel Isotopic Composition and Nickel/Iron Ratio in the Solar Wind: Results from SOHO/CELIAS/MTOF |
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Authors: | R Karrer P Bochsler C Giammanco F M Ipavich J A Paquette P Wurz |
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Institution: | (1) Physikalisches Institut, University of Bern, Bern, Switzerland;(2) Department of Physics, University of Maryland, College Park, MD, USA |
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Abstract: | Using the Mass Time-of-Flight Spectrometer (MTOF)—part of the Charge, Elements, Isotope Analysis System (CELIAS)—onboard the
Solar Heliospheric Observatory (SOHO) spacecraft, we derive the nickel isotopic composition for the isotopes with mass 58,
60 and 62 in the solar wind. In addition we measure the elemental abundance ratio of nickel to iron. We use data accumulated
during ten years of SOHO operation to get sufficiently high counting statistics and compare periods of different solar wind
velocities. We compare our values with the meteoritic ratios, which are believed to be a reliable reference for the solar
system and also for the solar outer convective zone, since neither element is volatile and no isotopic fractionation is expected
in meteorites. Meteoritic isotopic abundances agree with the terrestrial values and can thus be considered to be a reliable
reference for the solar isotopic composition. The measurements show that the solar wind elemental Ni/Fe-ratio and the isotopic
composition of solar wind nickel are consistent with the meteoritic values. This supports the concept that low-FIP elements
are fed without relative fractionation into the solar wind. Our result also confirms the absence of substantial isotopic fractionation
processes for medium and heavy ions acting in the solar wind. |
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Keywords: | Sun: solar wind Sun: elemental composition Sun: isotopic abundances |
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