Profiles of the original PM and UPM for Model B. Panels a) and b) show Γ₁ and V_g, respectively, as functions of the acoustic radius T_g. The dotted vertical lines indicate the locations of the Γ₁ bumps due to the HeII and the H ionizations. Panels c) and d) show the second difference for ℓ = 0–2 and the frequency difference between PM and UPM for the radial modes, respectively, as functions of the frequency.