Studies of Ionospheric Structures and Their Effects on Systems

This is a comprehensive investigation of the basic ionospheric processes which produce plasma density structuring. The emphasis of the research efforts was on understanding the formation and evolution of large-scale structures and the embedded km-scale irregularities that disrupt world-wide Air Force communication and navigation systems. Measurement of the temporal variability of a Sun-aligned arc electrodynamics was conducted with the Sondrestrom radar. It was demonstrated experimentally that traveling convection vortices and large plasma jets are able to form large-scale polar cap patches. The analysis of latitudinal profiles of TEC, obtained between 1800 and 2000 LT, indicated that equatorial spread-F develops when there is a sharp increase of TEC in the crests of the anomaly and a decrease near the trough. We have conducted a correlative study using the neutral winds and the irregularity drifts measured near the magnetic equator to show that most of the time drift and wind are closely coupled. On days when the coupling was not perfect there existed large wind gradients. Using two imagers displaced in longitude by 800 km we were able to perform the first simultaneous observations of the cusp aurora and to determine the response of the whole aurora to changes of the IMF. The original document contains color images. All DTIC reproductions will be in black and white.