Validation of First-Principles Model Calculations of the Upper Atmosphere.

Because of its effects on human activity, mostly through effects on every type of radio signal, it is important to understand the ionosphere and to understand its coupling with the Thermosphere and other atmospheric regions. These effects are often considered under the umbrella of space weather. The purpose of this project was to extend several aspects of our understanding of the ionospheric F region. The techniques used were a combination of comprehensive observations with incoherent scatter radars and detailed comparisons of such observations to simulations made with first principles models of the ionosphere. Three inputs to these models were examined electron heat flux, soft particle precipitation, and meridional winds. Procedures were developed to obtain, manipulate, and display the radar data. A first principles model was developed that places more emphasis on the topside F region than previously. This model was used to examine the cause of an anomalous F region maximum sometimes reported at mid latitudes. The cause was found to be a particularly strong meridional winds. However, to properly account for the maximum, the rate of collisions between the dominant ions and neutrals had to be increased by 70. The tools are now in place to perform a number more detailed comparisons.