List of Footnotes

1 Erratum 2009-04-15: corrected +P (∇ ⋅u) to − P (∇ ⋅u )
2 1.5D denotes the case when considering each column in a 2D or 3D model as a separate entity and, thus, ignoring all non-vertical radiative transfer.
3 We note that the equivalent widths quoted in Asplund et al. (2004Jump To The Next Citation Point) are not measured from the observed spectrum but theoretical values from the best-fitting 3D non-LTE line profiles.
4 The solar Ne and Ar contents are not inferable from the photospheric spectrum. Instead these abundances are deduced from the coronal Ne/O and Ar/O ratios coupled with the photospheric O abundance, assuming that these ratios are the same in the photosphere and the corona.
5 In their analysis of the C, N, and O, Grevesse and Sauval (1998) allowed for modifications of the temperature structure of the Holweger and Müller (1974Jump To The Next Citation Point) model in order to remove otherwise unavoidable trends with excitation potential and line strengths for certain species, see also Grevesse and Sauval (1999) for further details.