The space spectrum of convective instability

Growth rates are obtained for convective disturbances propagating in an atmosphere with a linear variation of entropy. The dispersion equation for small-scale disturbances in the parabolic entropy diagram case is considered by means of the WKB-approximation. It is shown for that case that the small-scale disturbances are reflected inside the convective zone and so cannot be observed at the Sun's surface. If the atmosphere is polytropic, it is shown that the small-scale disturbances can easily reach the sun's surface.