p- and g-mode cavities (propagation diagram)

What you are seeing: where a stellar oscillation actually lives. A pulsating cross-section shows the mode displacement field (degree $\ell$): large where the mode propagates, evanescent where it cannot. A low-frequency mode is trapped in the radiative-core g-cavity, a high-frequency mode in the acoustic-envelope p-cavity, and an intermediate one is a mixed mode in both. The linked propagation diagram carries $N$, $S_\ell$ and $\omega$ with the cavities shaded, and the mode energy split between the two cavities is read out.