Contraction radial velocity field V_f, Eq. (19), normalised to the top value V₀ and plotted as a function of radius r. The lines (from light to dark) show the weakest to the strongest density contrasts between the inner and outer spheres, which are respectively ρ_i/ρ₀ = 1.75, 10.8, 20.9, and 60.2. The contraction radial velocity field in the Boussinesq case given by Eq. (20) (i.e. corresponding to a density ratio of 1) is plotted as a dashed line as a reference.