Comparison of the square of the Lamb (﹩{S}_{{\ell }}^{2})﹩ and Brunt–Väisälä (N²) frequencies for ℓ = 1 modes of the original and relaxed MESA models. The upper panel plots these data as a function of fractional mass M_r/M. The lower panel shows the relative differences, defined as ﹩E({N}^{2})=({N}_{\mathrm{relax}}^{2}-{N}_{\mathrm{orig}}^{2})/{N}_{\mathrm{orig}}^{2}﹩, and similarly for ﹩{S}_{{\ell }}^{2}﹩.