Comparison of the total modelled (black) and observed brightness (magenta), B^X, of each emission line. The stacked bars show the contribution from each neutral species and emission process. The same colour code as Fig. 4 is used. The error on the observed brightness is derived from the integration of the FUV spectra. The error on the modelled brightness is from the temporal variation of the electron flux and column density, as well as a 20% uncertainty in the neutral composition. In cases 1–8, where the observed OI1356 brightness is used to fit the total neutral column density (see Sect. 3.2), the error on the modelled OI1356 brightness is included in the error of the other modelled emission brightnesses.