Wave‐induced fluctuations in ionospheric electron content: A model indicating some observational biases
TL;DR: By assuming that a plane atmospheric wave acts on a plane-stratified F layer in the presence of a constant geomagnetic field, this paper derived an expression for the resulting perturbations in total columnar electron content as a function of wave and ionospheric-layer parameters and of the orientation of the column through the ionosphere.
Abstract: By assuming that a plane atmospheric wave acts on a plane-stratified F layer in the presence of a constant geomagnetic field, we derive an expression for the resulting perturbations in total columnar electron content as a function of wave and ionospheric-layer parameters and of the orientation of the column through the ionosphere. Although idealized, the model not only correctly predicts the order of magnitude of the observed perturbations but also makes visible much of the physics that determines the magnitude of wave-induced total-content fluctuations observed by using satellite transmissions through the ionosphere. Geomagnetic constraints on ion motion and a tendency for total-content fluctuation to be greatest when the ground-satellite path lies in a surface of constant atmospheric wave phase combine to introduce strong experimental biases that favor the observation of some waves and prevent the observation of others. The effects of these biases must be fully removed before total-content measurements can yield the statistical properties of atmospheric waves at ionospheric heights that may be useful in locating wave sources or in characterizing the dynamic state of the ionosphere.
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TL;DR: The theoretical and observational evidence concerning the global propagation of atmospheric gravity waves is reviewed in this article, with special emphasis on the waves generated in the auroral zones, and it is concluded that the only natural sources of large-scale TIDs are in the ionospheric zones.
392 citations
TL;DR: In this article, the authors review the theory of acoustic-gravity waves, the interaction of such waves with the ionosphere, the experimental support for the existence of acoustic gravity waves in the upper atmosphere, and the role played by acoustic gravity wave in thermospheric dynamics.
Abstract: 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.
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Cites background from "Wave‐induced fluctuations in ionosp..."
...The ionospheric photochemical balance can be significantly altered by neutral waves at lower altitudes (below 250 km), that is, in weakly ionized medium (George & Hooke, 1970)....
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TL;DR: In this paper, the F2 region ionospheric response to individual internal gravity waves is calculated as a function of the azimuth of wave propagation, and the response is shown to be highly anisotropic, with the anisotropy itself depending on the wave parameters, the geomagnetic dip and the prevailing ionization density gradient.
Abstract: The F2 region ionospheric response to individual internal gravity waves is calculated as a function of the azimuth of wave propagation. This response is shown to be highly anisotropic, with the anisotropy itself depending on the wave parameters, the geomagnetic dip, and the prevailing ionization density gradient. Because the ionization density gradient changes with time of day and season, the ionospheric response and hence the traveling ionospheric disturbance statistics themselves should exhibit corresponding diurnal and seasonal variations. The physical basis for the anisotropy of the ionospheric response is discussed.
116 citations
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TL;DR: In this paper, the proper interpretation of irregular motions in the upper atmosphere has been investigated by a variety of techniques, but their proper interpretation has yet to be established. But their proper meaning has not yet been established.
Abstract: Irregularities and irregular motions in the upper atmosphere have been detected and studied by a variety of techniques during recent years, but their proper interpretation has yet to be established...
1,886 citations
TL;DR: In this article, a perturbation treatment is used to determine the nature and magnitude of the effects of internal atmospheric gravity waves on the ambient rates of production, chemical loss, and motion of the ionization.
337 citations
TL;DR: In this article, a review of the observational evidence for the upper atmosphere is presented, in groupings determined by the physical processes that are thought to be operative, and corresponding theories are measured against it.
Abstract: The atmosphere above 80 km exhibits a wide range of dynamical phenomena. These are largely hydrodynamic in nature, and their sources of energy are likely to lie principally at lower levels. The regions are ionized, however, and hydromagnetically controlled motions also exist. They are generated from above as well as below.
The observational evidence is reviewed broadly here, in groupings determined by the physical processes that are thought to be operative, and the corresponding theories are measured against it. Many shortcomings are disclosed and assessed, and profitable avenues for future research are tentatively explored. Several areas are indicated in which the dynamical processes modify other features of the upper atmosphere, but these are not analysed in detail.
333 citations
TL;DR: In this article, a network of CW Doppler sounders was used to detect ionospheric motions observed with a network-of-CW Dopplers. The motions of each type are attributed to various kinds of atmospheric waves that interact with the ionosphere.
293 citations
TL;DR: In this paper, the horizontal movements of travelling ionospheric disturbances recorded on a single radio frequency from April 1948 to March 1957 are analyzed for seasonal and diurnal variations of occurrence and of direction and speed of travel.
Abstract: Observations of the horizontal movements of travelling ionospheric disturbances recorded on a single radio frequency from April 1948 to March 1957 are analysed for seasonal and diurnal variations of occurrence and of direction and speed of travel. Recording was mainly in daylight hours but some limited night results are included. The average number of disturbances recorded was six per day over the period. Observing accuracy and significance of the deduced data are discussed. The frequency of occurrence has a diurnal variation with a marked midday maximum and a seasonal variation with minima at the equinoxes.
163 citations