Distribution of hydrogen and helium species against radial distance predicted by models #3 (top panel) and #4 (bottom panel). The grey solid line gives the total numerical density of all hydrogen species, for reference. The blue lines show the species of atomic hydrogen (solid for neutral H, dashed for H⁺, and dash-dotted for H⁻), the green lines show molecular hydrogen (solid for neutral H₂ and dashed for H⁺), the violet dashed line shows , and the orange lines show helium species (solid for neutral He, dashed for He⁺, and dotted for He⁺+).