Top: Number density profiles of neutral species with a basal H₂O/H₂ of 0.001, stellar EUV flux of $1000F_{\mathrm{EUV}}^{\oplus }$, M_p = 5M_⊕, and g = 4 m s⁻². The inset panel shows details near the base of the flow. Middle: Predicted number density profiles of ions. Bottom: Contribution of these species to cooling rates. “Radiative heating" is the heating rate by adsorption of X-rays and UV, and “chemical expense" is the energy used by chemical reactions such as photolysis.