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Keywords:

  • Aeronomy: Winds;
  • Ionosphere: Disturbances;
  • Ionosphere: F-Region;
  • Ionosphere: Wave Propagation

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.