Regions where the tidal response of the radiative layer is dominated by the gravitational (blue area) and thermal (red area) components of the forcing in the zero-frequency limit (σ → 0). The logarithm of the ratio η given by Eq. (79) (black solid line) is plotted as a function of the star-planet distance r_⋆ (AU) in logarithmic scale. The blue dashed line designates the critical distance at which the two components are of the same order of magnitude (η ≈ 1).