The oscillations of late-type main-sequence stars are driven by stochastic fluctuations of the convection envelopes. The precise nature of the interaction between the convective eddies and the oscillations is not well understood; even the basic scaling between oscillation frequency and amplitude and the spectrum of the turbulence is uncertain. By measuring the temporal variations of the amplitudes and the phase relations amongst oscillation modes of like degree and azimuthal order for a variety of stars, we should extract the basic scaling factors that will help us to determine what the principal interactions that dominate the convection-pulsation coupling are. This can be used as a diagnostic for studying the statistical properties of the convection at the location where the oscillations are excited (believed to be in the layers immediately below the photosphere).
Envelope convection begins as stars cross the granulation boundary in the H-R diagram (see Fig. 1.1). The location of this boundary is not well known at present (Gray and Nagel 1989). STARS has the capability of measuring the presence or absence of several different indicators of convection near that boundary: granulation, stellar oscillations, non-radiative chromospheric heating, and magnetic fields. This would open the possibility of studying the sequence of processes taking place as stars develop convective envelopes, which would be of great importance for our understanding of magnetic braking and astrophysical dynamos.