Semiclassical approximation for low-degree stellar p modes - III. Acoustic resonances and diagnostic properties of the oscillation frequencies

We extend the classical approximation for low-degree acoustic oscillations to take account of the effects of wave resonances associated with the partial reflection of waves at internal boundaries in the stellar interior. We consider explicitly the effect of a rapid density variation at the boundary of the convective core on the small frequency separations, and the reflection of waves at the base of the outer convective envelope, observable in the 'surface phase-shift' function. We describe a technique that allows us to infer the 'surface phase-shift' function, known to be a valuable diagnostic tool in solar seismology, from frequency measurements limited to p modes of low degree only.