Verification of Eq. (1) for a set of 120 modes with the · being the 40 radial modes, the × being the 40 dipolar modes and the + being the 40 quadrupolar modes. The left plot illustrates this verification for the (ρ,c²) couple when no scaling is applied to c² whereas the right plot illustrates the same verification for the (ρ,c²) couple when scaling is applied to c², as well as the (ρ,Γ₁) couple where no scaling is needed.