Fig. 1. Cut along the central plane (i.e. the plane spanned by the flux-tube axis and the line of sight) through arrays of two flux-tube models, showing the flux-tubes shaded), and a sample of rays in the central plane, along which line profiles were calculated. For the line profile calculations more rays were used. The thick line delineates the continuum optical depth unity () level at the appropriate viewing angle. The thick vertical bar on the right border frame indicates roughly the height range over which Fe I 5250.2 Å is on average formed. a Model D with km, b model E with km. Profiles are also calculated along rays lying within other planes parallel to the central plane, as described in the text and illustrated by Bünte et al. (1993). The angle between the rays and the flux-tube axis is the same in both figures, and corresponds to . c and d show the same models as Figs. 1a and b, respectively, but now with rays having an inclination corresponding to .