PHASES AND AMPLITUDES OF ACOUSTIC-GRAVITY WAVES .2. THE EFFECTS OF REFLECTION

We study wave reflection caused by the temperature stratification of t he solar atmosphere, assumed to be a succession of two layers of diffe rent temperatures and radiative decay times. Considering waves which p ropagate energy upward in the atmosphere, we compute the complex ampli tude reflection and transmission coefficients and investigate the effe cts that reflection introduces on the phases of acoustic-gravity waves . In the evanescent region of the k(x) - omega diagram, between the La mb waves and the acoustic cut-off frequency, the reflection coefficien t is small, in particular zero on the fundamental mode. Therefore, in this region, the reflected wave has a small amplitude and its superpos ition to the incident wave does not affect the latter in a significant way. In particular, the T - V phase differences of the total wave are very similar to those of the incident wave. Furthermore, a heuristic formula is presented which describes the observed coexistence of two d ifferent phase regimes between velocity and intensity oscillations in the evanescent area above the fundamental mode.