Solar Wind Iron Isotopic Abundances: Results From Soho/Celias/Mtof

The MTOF sensor uses time of flight measurements in a harmonic potential region to identify elements and isotopes in the solar wind with excellent mass resolution. The combination of MTOF's large bandwidth electrostatic deflection system and the 3-axis stabilized orientation of SOHO results in excellent counting statistics. We report relative abundances of the iron isotopes with mass 54, 56 and 57 amu. Since these isotopes are chemically identical, we expect little fractionation either in the solar wind or in the instrument, resulting in relatively small estimated uncertainties. Our results agree, within the measurement uncertainties, with terrestrial values.