Is the FIP effect present inside solar photospheric magnetic flux tubes ?

The first determination of the elemental composition in the photospheric layers of solar magnetic flux tubes is described. Stokes I and V profiles of 13 elements observed in solar active region plage and in the network are analysed. The abundances are obtained for elements with high (C, O) and low (Al, Ca, Cr, Na, Ni, Sc, Si, Ti, Y, Zn) first ionization potential (FIP) in order to investigate to what extent the abundance anomalies observed in the upper solar atmosphere (FIP-effect) are already present in the photospheric layers of flux tubes, which are the source of much of the gas in the upper atmosphere. Various sources of error are considered and the uncertainties introduced by them are estimated. There are hints of a weak FIP-effect in the flux tubes, corresponding to an overabundance of a factor of 1.1–1.2 of the low-FIP elements relative to high-FIP elements, as compared to the quiet photosphere. However, our data set a firm upper limit of 1.3–1.6 on this factor, which is well below the enhancement seen in many parts of the upper solar atmosphere.