Mean absorption spectra between T₂ and T₀ of night 1. The red curve was computed using the stellar grid that best matched the observed F_out using the additional chromospheric absorption. The other curves are computed using the F_out from the best fit and F_in’s from modified stellar spectral grids. As a reference for the best fit, n_c = 7.54 × 10¹¹ atoms cm⁻³. These specific values should only be regarded to get a sense of how the sodium lines were modified, and not as exact values for this specific system.