Ionization balance of selected elements iron (Fe), phosphorus (P), and carbon (C) for FASTWIND models “O1” (top panels), “O2” (middle panels), and “O3” (lower panels) with parameters according to Table 1. Plotted in each panel are number density ratios log n_j/n_i for ion stage j of species i, with n_i the total element abundance, as function of a radius coordinate log¹⁰(r/R_* − 1). Blue lines are models “thick” including full effects of porosity in physical and velocity space; red lines are models “thin” assuming optically thin clumping; black lines are models “smooth” without any wind clumping. For iron (left panels), phosphorus (middle panels), and carbon (right panels), the displayed states are given in the upper right of each panel; solid lines then show the ion fraction in the lowest considered state j, the dotted lines show state j + 1 and the dashed ones j + 2. (For example the top left panel thus shows Fe 3⁺ − 5⁺ = Fe IV − VI in models O1 “thick” (blue), “thin” (red) and “smooth” (black), where solid lines are ion fractions of Fe IV, dotted lines of Fe V, and dashed lines of Fe VI.)