Phases and amplitudes of acoustic-gravity waves. 2: The effects of reflection
Abstract
We study wave reflection caused by the temperature stratification of the solar atmosphere, assumed to be a succession of two layers of different temperatures and radiative decay times. Considering waves which propagate energy upward in the atmosphere, we compute the complex amplitude reflection and transmission coefficients and investigate the effects that reflection introduces on the phases of acoustic-gravity waves. In the evanescent region of the kx - omega diagram, between the Lamb waves and the acoustic cut-off frequency, the reflection coefficient is small, in particular zero on the fundamental mode. Therefore, in this region, the reflected wave has a small amplitude and its superposition 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 heruisitic formula is presented which describes the observed coexistence of two different phase regimes between velocity and intensity oscillations in the evanescent area above the fundamental mode.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- November 1993
- Bibcode:
- 1993A&A...278..617M
- Keywords:
-
- Gravity Waves;
- Hydrodynamics;
- Solar Atmosphere;
- Sound Waves;
- Temperature Gradients;
- Wave Reflection;
- Adiabatic Conditions;
- Perturbation;
- Radioactive Decay;
- Solar Oscillations;
- Solar Temperature;
- Solar Physics