Acoustic-gravity waves near the temperature discontinuity in the solar atmosphere

The propagation of atmospheric waves near the transition region in the solar atmosphere is studied. The dispersion relation for surface waves propagating at the temperature discontinuity in a two-layer model atmosphere is derived and analyzed. Exact solutions are found for this relation. They include various modes that propagate along the boundary. One type of wave has a dispersion relation of the same form as that of deep water waves. These waves can propagate if their frequency exceeds omega(g), the Brunt-Vaisala frequency for the lower layer. The frequencies of other surface waves are equal to omega(g) frequencies of each of the two layers. It is also shown that a squeezed mode can propagate near the boundary. This mode is characterized by the absence of horizontal velocity and pressure perturbations. The results are used to interpret observational data for the solar atmosphere.