Power spectra E_ℓ at depths r = [0.243, 0.485, 0.728] R_★ for the Full model (first row), the EnvCZ model (second row), and the CoreCZ model (third row). The degree-dependent cut-off frequency between the standing modes and the progressive waves is shown on every panel with a dashed black line. In the first two rows, the limit frequency where intermediate- and high-degree modes are unable to form in the Full model while visible in the EnvCZ model is indicated with the dotted black line. The border colour of the panels is different for each row in order to guide the eye (each colour corresponds to a model: orange, blue, and yellow for the Full, EnvCZ, and CoreCZ models, respectively).