Trapping parameter as described by the true model, ζ_mod (Eq. (2)) as a function of the true frequencies ν_mod (dashed black line and black circles). Red circles represent the trapping parameter ζ_as as approximated by Eqs. (11)and (8)and using ν_as for the mode frequencies as determined by Eq. (6). The scaled period spacing ΔP/ ΔΠ₁ between any two consecutive true frequencies ν_mod,1 and ν_mod,2 is plotted at the abscissa (blue crosses). ΔP_ν represent the interpolated value of the two adjacent period spacings around each frequency ν_mod (green crosses).