Heating and cooling contributions in the middle and upper atmosphere (i.e. at pressures lower than CLOUDY’s density limit) of WASP-178b. Top: Contribution to the total heating as a function of pressure. At each pressure bin, the plot shows the three most important heating processes. The main heating processes are hydrogen photoionisation (red; photoionisation of HI lying in the ground state), metal line absorption (blue), H⁻ absorption (green), photoionisation of hydrogenic species (magenta), collisions with H₂ (brown), and Compton heating (i.e. electron absorption; yellow). Bottom: Contribution to the total cooling as a function of pressure. At each pressure bin, the plot shows the three most important cooling agents. The main cooling agents are Mg (red), Ca (blue), C (green), ${\mathrm{H}}_2^{+}$ (magenta), H (brown), S (orange), HD (i.e. hydrogen deuteride; yellow), Na (grey), and Si (light blue). Metal line absorption (primarily from FeII) and Mg line emission are the primary heating and cooling mechanisms, respectively.