Abstract—

The propagation of evanescent acoustic-gravity waves in the atmosphere with an arbitrary altitude temperature profile is investigated. The possibility of the existence of two types of evanescent wave modes in a vertically nonisothermal atmosphere is shown. The first type is the f-mode in which the dispersion does not depend on the altitude inhomogeneity of temperature and, therefore, is carried out at any altitude level of the nonisothermal atmosphere. The second type is a recently discovered \(\gamma \)‑mode in which the dispersion depends on the altitude temperature gradient and can be fulfilled only at certain altitude intervals. The possibility of realizing the f- and \(\gamma \)- modes in the Earth’s atmosphere is considered, taking into account the model altitude temperature profile. It is shown that these modes can exist at the heights of local temperature extremes in the atmosphere. Moreover, they are realized only in a narrow range of spectral parameters for which the conditions for a decrease in the wave energy above and below the level of their propagation are satisfied. For the f-mode, this energy condition is fulfilled at the altitudes of the local temperature minima, while that for the \(\gamma \)-mode is at the altitudes of the local maxima. Recommendations are given regarding the possibility of observing these modes in the atmosphere of the Earth and the Sun. In the Earth’s atmosphere, the f-mode can presumably be observed near the mesopause with the characteristic wavelength \({{\lambda }_{x}} \approx 75\,{\text{km}}\) and in the solar atmosphere at the heights of the chromospheres with \({{\lambda }_{x}} \approx 1600\,{\text{km}}\). The period of the f‑mode propagating in the region of the temperature minimum slightly exceeds the Brent-Väisälä period at this altitude. In the Earth’s atmosphere, the \(\gamma \)-mode can be realized in the regions of maximum temperature, for example, at the height of the stratopause with \({{\lambda }_{x}} \approx 100\,{\text{km}}\) and a period slightly larger than the Brent-Väisälä period at the altitude of its propagation.

中文翻译：

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非等温大气中的渐逝声重力波模式

摘要-

研究了具有任意高度温度剖面的大气中倏逝声重力波的传播。显示了在垂直非等温大气中存在两种渐逝波模式的可能性。第一种类型是f模式，其中色散不取决于温度的高度不均匀性，因此在非等温大气的任何高度水平上进行。第二种类型是最近发现的\(\gamma \)模式，其中色散取决于海拔温度梯度，并且只能在特定的海拔间隔内实现。实现f - 和\(\gamma \)的可能性- 考虑地球大气中的模式，同时考虑模型海拔温度剖面。结果表明，这些模式可以存在于大气中局部极端温度的高度。此外，它们仅在狭窄的光谱参数范围内实现，为此，在其传播水平之上和之下波能减少的条件得到满足。对于f模式，该能量条件在局部温度最小值的高度处得到满足，而对于\(\gamma \)模式，则在局部最大值的高度处满足。给出了关于在地球和太阳大气中观察这些模式的可能性的建议。在地球大气层中，f-mode 大概可以在具有特征波长\({{\lambda }_{x}} \approx 75\,{\text{km}}\)的中层顶附近以及在色球层高度的太阳大气中观察到与\({{\lambda }_{x}} \approx 1600\,{\text{km}}\)。在最低温度区域传播的f模式周期略超过该高度的 Brent-Väisälä 周期。在地球大气中，\(\gamma \) -模式可以在最高温度区域实现，例如，在平流层顶的高度\({{\lambda }_{x}} \approx 100\ ,{\text{km}}\)和在其传播高度上略大于 Brent-Väisälä 周期的周期。