Properties of a cutout along the x-axis of the lower part of the EB (indicated as a white box in Figs. 1 and 3). Top row: temperature T, mass density ρ, and electron number density n_e are shown on a log scale. Bottom row: ratio of the number density of He I, He II, and He III to the total number density of helium n_tot are shown on a log scale. The black and white markers show the position of the He I D₃ profile shown in Figs. 6 and 8 at locations L_em (see Fig. 5) and h_em (see Fig. 8).