F-region dynamics

The U.S. research efforts in the last four years, relating to an understanding of upper atmosphere or thermosphere and F-region dynamics are reported. Simultaneous measurements of atmospheric parameters from the Atmosphere Explorer satellites were used in photochemistry and photoenergetics studies. Studies of the magnetosphere as a major source of energy and momentum for the thermosphere are outlined. Time-dependent ionosphere models which describe the thermal structure, composition, photoelectron spectrum, and airglow emissions in F-regions are discussed. Solar tides, magnetic disturbances, and gravity waves in the thermosphere are considered. It is noted that planetary explorations will help to understand scientific problems of the space environment.