Iron abundance in the solar photosphere. Application of a two-component model atmosphere

Abstract

A realistic two-component model of the quiet Sun is used to determine the solar abundance of iron from the inversion of a number of Fe I and Fe II spectral lines for which accurate atomic parameters (oscillator strengths, central wavelengths, and collisional broadening cross sections) exist. From 33 Fe I lines we infer an abundance of AFe = 7.43 ± 0.06, whereas we estimate AFe = 7.45 ± 0.08 from 10 Fe II lines. These values are in excellent agreement with the results of analyses based on realistic 3 hydrodynamical simulations of the solar granulation, and imply a low photospheric iron abundance. We investigate the effects of convective motions and granular temperatures and conclude that both are important for reliable abundance determinations. For Fe I lines, the effects of convective motions can be simulated by using a microturbulent velocity of about 1 km s-1, whereas it is possible to account for temperature inhomogeneities by adopting an average temperature stratification which is cooler than the Holweger & Müller model in the upper layers.