Cartoon illustrating the geometry of the radiation transfer in our model. The bottom right of the cartoon is the centre of the planet and the incoming stellar radiation is travelling horizontally from left to right. The inner black region is the planet and the shaded region is the upper atmosphere. The simulation domain of our 1D atmosphere model, illustrated with the blue region, is a region that is pointing radially outwards from the planet centre. The angle θ is the zenithangle. To calculate the stellar XUV and IR spectra at any given point, we perform radiation transfer along the dashed black line.