Radially trapped overstable convective modes within a polytropic solar interior

ABSTRACT We study overstable and unstable gravito-inertial waves in a weakly unstable polytropic atmosphere representing solar convection zone. We consider wave modes propagating at a small angle to the zonal direction near the equatorial region of the Sun. We find that the coriolis force plays an important role in stabilizing low radial order, long wavelength convective modes which otherwise would be unstable in the absence of rotation. Focusing solely on naturally trapped waves in the radial direction, we also compare the properties of these low frequency gravito-inertial wave modes with corresponding wave modes in a neutrally stable polytropic atmosphere in different sized finite domain. We find that the eigenfrequencies of gravito-inertial wave modes in a weakly unstable polytropic atmosphere are lower than those in a neutrally stable atmosphere, and that their propagation is confined to a narrower wavenumber range. These eigenfrequencies and the range of wavenumbers increase slightly as the angle of propagation increase.