Physical structure of PN when T_eff ≃ 50 500 K, the fast-wind speed v = 1031 km s^-1, and the model age is 4246 yr: a) the electron temperature T_e; b) the total ion density n_A; c) the effective charge Z and the diffusion coefficient D. The electron temperature and the total ion density are shown at three scales as indicated in each panel. Values of model HC (HC_H) are drawn with black (magenta) lines; for the diffusion coefficient the lines are blue (light blue). The heat-conduction flux of model HC is saturated in the region that is marked with a blue box. The chemical discontinuity between the H-rich nebula and the H-deficient inner parts is in the bubble-nebula interface. All lines are drawn as histograms to emphasize individual gridpoints. The fast wind (bubble) is drawn on a medium gray (light gray) background for model HC.