Reference radial brightness (left) and H (right) profiles for 1998 and 2011 observations. Our 1998 and 2011 ambient atmosphere profile is identical to that of Voyager 2, except for 1998, reference ambient H profile is 1.5 × Voyager 2 base ambient H profile. For both 1998 and 2011 model atmospheres, along with Voyager 2 hot H, we introduce new hot H population (H^*). The reference H^* Chapman profiles shown in this figure have parameters for 1998 as ${\left(T,z_{\max },H,N\right)}_{{\text{H}}^{*}-1998}$ = (0.3 eV, 3000 km, 5000 km, 0.075% of Voyager 2 base ambient H) and for 2011 as ${\left(T,z_{\max },H,N\right)}_{{\text{H}}^{*}-2011}$ = (0.3 eV, 3000 km, 5000 km, 0.05% of Voyager 2 base ambient H). See text for the meanings of parameters. The reference radial brightness profiles for 1998 and 2011 observations have ${\chi }_{\nu }^2~3$ and 1, respectively.