Internal waves are waves propagating inside a liquid or gas .
For the emergence of internal waves need a drop in density. In a liquid, a small density difference may occur due to temperature and salinity changes with depth. Since this difference is not large, the internal waves have a low propagation velocity. On the other hand, the amplitude of internal waves can be large, since they do not require large energy to generate them. The simplest and most observable example of internal waves is internal waves in water.
Contact with surface waves
Internal waves create temporary currents, including on the surface of the water . Therefore, if the surface waves go against this flow, then they are shortened and the surface of the water in this place looks dark and rough. If the surface waves go along the flow, then they are extended and the surface of the water in this place looks smooth. In this case, the amplitude reduction of the surface waves does not occur .
When the wind direction changes, the direction of the surface waves changes, and the weak wind has no effect on internal waves. Therefore, the picture of light and dark areas can quickly change with a change in wind direction.
Internal waves, approaching the surface, cause the redistribution of surfactants , which in turn affect the reflection coefficient of electromagnetic, including light, waves, which makes it possible to detect internal waves by remote methods, for example, they are visible from space.
Internal waves, compared to ordinary surface waves, have a number of surprising properties. For example, the group velocity of internal waves is perpendicular to the phase, the angle of reflection of internal waves from the slope is not equal to the angle of incidence.
Literature
- Glinsky N. T. Internal waves in the oceans and seas / Ed. ed. R.V. Ozmidov .. - M .: Science , 1973. - 128 p. - ( Problems of modern science and technical progress ). - 8 500 copies (region)