Effect of Lyman-continuum irradiation from an O3 and a B0 star at a distance of 0.5 pc and from the ISRF compared to the effect of the thermal ionisation on giant gas planet or young brown dwarf atmospheres (top panel), and on old brown dwarf atmospheres (middle panel). The threshold f_e > 10⁻⁷ (thin solid black line) marks the point above which the atmospheric gas becomes partially ionised. The cloud particle number density, n_dust (cm⁻³), is plotted as comparison to where the cloud layer is located relative to the LyC gas ionisation depth.