Acoustic-gravity waves with height-independent amplitude in the isothermal atmosphere
Рубрика:
| 1Cheremnykh, OK, 1Fedorenko, AK, Cheremnykh, OS, 2Kronberg, EA 1Space Research Institute under NAS and National Space Agency of Ukraine, Kyiv, Ukraine 2Max Planck Institute, Göttingen, Germany |
| Kinemat. fiz. nebesnyh tel (Online) 2023, 39(5):54-64 |
| https://doi.org/10.15407/kfnt2023.05.054 |
| Язык: Ukrainian |
Аннотация: Acoustic-gravity wave modes in the Earth’s thermosphere, the amplitude of which does not depend on height, are theoretically investigated in this paper. The stimulus for these studies is satellite observations, according to which the amplitudes of acoustic-gravity waves in the polar thermosphere do not show dependence on height in the altitude interval of 250...450 km. It is shown that the propagation of acoustic-gravitational wave modes with the height-independent amplitude should be considered as an oscillatory process that occurs simultaneously at two natural frequencies. The dispersion equation for these waves was obtained. On the frequency-wave vector diagnostic diagram, the dispersion dependence of waves with constant amplitude is in the area prohibited for free propagation. It separates horizontally propagating waves in which the amplitude in the vertical direction increases from waves in which the amplitude decreases in the vertical direction. Solutions were found for the perturbed quantities in the two-frequency mode of oscillations. It is noted that the superposition of several such modes can lead to the emergence of complex resulting motions close to turbulent ones. It is shown that there is a selected quasi-harmonic mode with constant amplitude, which is characterized by a fixed frequency and wavelength. It was concluded that this kind of wave mode with height-independent amplitude of the perturbed values prevails in the observations in the Earth’s polar thermosphere. |
| Ключевые слова: acoustic-gravity wave, Earth’s thermosphere, two-frequency oscillation mode |
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