Global propagation of atmospheric gravity waves: A review

In this paper we review the theory of acoustic-gravity waves, the interaction of such waves with the ionosphere, the experimental support for the existence of such waves in the upper atmosphere, and the role played by acoustic-gravity waves in thermospheric dynamics. After a thorough discussion on the properties of acoustic-gravity waves in an ideal isothermal atmosphere, the effects produced by horizontal winds, sharp boundary discontinuities, and dissipative processes are discussed. The generation of these waves by stationary or moving sources is then treated. It is shown that the atmospheric response to a stationary impulse source can be described by the emission of three waves: acoustic, buoyancy, and gravity. These discussions are then followed by reviewing propagation effects in a realistic atmosphere for both free waves and guided waves. Recent numerical results are given. When acoustic-gravity waves propagate through the ionosphere, interaction between the wave and the ionosphere will take place. The physical processes involved in such an interaction are examined.

Acoustic‐gravity waves in the upper atmosphere

phase speeds of cH � 480–510 m/s, density perturbations as large as jr 0 /r j� 3.6–5% at z = 400 km, relative [O] perturbations as large as � 2–2.5% atz = 300 km, and total electron content perturbations as large as � 8%. This transfer of momentum from local, relatively slow, small scales at the tropopause to global, fast, large scales in the thermosphere is independent of geomagnetic conditions. The various characteristics of these large-scale waves may explain observations of LSTIDs at magnetically quiet times. We also find that this body force creates a localized ‘‘mean’’ horizontal wind in the direction of the body force. For the plume at 2120 UT, the wind is southward with an estimated maximum of vmax �� 400 m s � 1 that is dissipated after � 4h . We also find that the induced body force direction varies throughout the day, depending on the winds in the lower thermosphere.

https://www.cora.nwra.com/~vasha/VadasLiu2009.pdf

Generation of large-scale gravity waves and neutral winds in the thermosphere from the dissipation of convectively generated gravity waves

Using global positioning system (GPS) data taken from 350 dual-frequency GPS receivers in Southern California in 2002, we investigated two-dimensional maps of total electron content (TEC) perturbations with a time resolution of 30 s and a spatial resolution of 0.15°×0.15° in longitude and latitude to reveal statistical characteristics of medium-scale traveling ionospheric disturbances (MSTIDs). We found that MSTIDs can be categorized into three types. One type is daytime MSTIDs, which frequently occur in winter and equinoxes. Since most of the daytime MSTIDs propagated southeastward, we speculate that the daytime MSTIDs could be caused by atmospheric gravity waves in the thermosphere. A second type is nighttime MSTIDs, which frequently occur in summer. Nighttime MSTIDs propagate southwestward. This propagation direction is consistent with the idea that polarization electric fields could play an important role in generating nighttime MSTIDs. The third is dusk MSTIDs, which frequently occur in summer and propagate northwestward. Dusk MSTIDs could be caused by gravity waves originating from the sunset terminator because they have wavefronts almost parallel to the sunset terminator.

https://link.springer.com/content/pdf/10.1186%2FBF03352681.pdf

Statistical study of medium-scale traveling ionospheric disturbances observed with the GPS networks in Southern California

Atmospheric gravity waves similar to waves that occur on the surface of a body of water have been known since the nineteenth century, but their significance for the study of atmospheric dynamics has been realized only in the past ten years

Gravity Waves in the Atmosphere

The propagation of internal gravity waves in a model atmosphere with stratified neutral winds is studied. The waves are subjected to a ray-tracing analysis and, as a result, are grouped into three types: (1) those that penetrate the F region of the ionosphere, (2) those that are reflected, and (3) those that nearly reach the critical-layer condition and are absorbed. Examples of the three types of ray paths are shown. The traveling waves observed in the ionosphere are excited by the propagating acoustic-gravity waves launched at lower levels in the atmosphere. The characteristics of the waves, such as period and velocity, are dependent on atmospheric conditions, as well as on the nature of the source. Extensive computations show that neutral winds provide a directional filter effect as depicted in several contour plots. From Faraday rotation data taken during the summer of 1968, the characteristics of 13 traveling waves that were observed fit into the calculated contours reasonably well.

Group rays of internal gravity waves in a wind‐stratified atmosphere

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Group rays of internal gravity waves in a wind‐stratified atmosphere