Panel a: Lyα irradiance profiles reported in Figs. 6a and 12 of Fontenla et al. (1988; QS and AR, respectively), as well as profiles observed on April 17, 2009 (CH, Tian et al. 2009b), on October 28, 1996 (full disc, Lemaire et al. 2015) and in an equatorial CH at the central meridian between November 27 and 29, 1975 (Bocchialini & Vial 1996). Panel b: parametrised Lyα profiles from Kowalska-Leszczynska et al. (2018; IKL; at maximum and at minimum) and Auchère (2005). Each profile has been normalised to its total intensity.