First steps towards a solar wind 13C/12C ratio

The isotopic composition of the Sun provides information about the properties of the presolar nebula. One way to determine the solar isotopic abundances are spectroscopic observations of the solar surface. In the case of carbon previous measurements exploited that the rotation bands of the two stable carbon isotopes 13C and 12C in CO molecules are slightly different. The focus of this work is to determine the 13C/12C ratio in the solar wind for the first time by in situ measurements, because deviations of the isotopic composition in photospheric observations and solar wind measurements indicate fractionation processes in the chromosphere and the corona. Based on long term- data from the linear time-of-flight mass spectrometer SWICS (Solar Wind Ion Composition Spectrometer) mounted on ACE (Advanced Composition Explorer, at L1 since 1997) we present the first results and compare them with spectroscopic measurements.