Parameter δ (Eq. (36)) as a function of radius of curvature R. The black and red lines correspond to δ(0,ϵ₂) and δ(ϵ₁,0), respectively. The solid black thick line is δ(0,ϵ₂ = 0.01 Mm^-2) whereas the solid black thin line corresponds to δ(0,ϵ₂ = −0.01 Mm^-2) for the fundamental mode. The black dashed lines are the same but for the first overtone. The solid red line is δ(ϵ₁ = 0.1 Mm^-1,0) for the fundamental mode and the dashed red line is the same for the first overtone. The remaining parameters are L = 100 Mm, l = 5 Mm, c_sc = 200 km s^-1, and χ = 100, as in Fig. 3.