Top left: ratio of the n = 2 and n = 1 level populations for neutral hydrogen (bottom x-axis) as a function of atmospheric pressure (left y-axis) and planetary radius (right y-axis) computedwith Cloudy in NLTE (solid line) and using the Boltzmann equation (i.e. LTE; dashed line) considering the TP model number 025, shown by the red line (red top x-axis). Top right: line optical depth as a function of atmospheric pressure for Hα (solid line) and Hβ (dashed line) computed with Cloudy considering the TP model number 025. Both hydrogen lines form mostly between 10⁻⁵ and 10⁻⁸ bar. Bottom: same as top panels, but for the TP model number 108.