The Fe/O elemental abundance ratio in the solar wind

We analyze the Fe/O elemental abundance ratio in the solar wind from SOHO/CELIAS/CTOF data. Analyzed in different solar wind regimes this ratio is indicative of the strength of the FIP fractionation process because iron is a low FIP element and oxygen is a high FIP element. It is investigated whether there is a significant fractionation of the Fe/O ratio in the coronal hole solar wind. For the first time, to our knowledge, we attempt to eliminate the influence of model-dependent parameters on the derivation of the photospheric Fe/O ratio thereby increasing the accuracy of its determination. The Fe/O ratio in coronal hole solar wind is slightly higher than in the photosphere. Even with our optimistic estimates of the uncertainties of the photospheric Fe/O ratio the observed fractionation is only marginally significant.