This proposal will investigate the spatial extent and temporal evolution of the ionospheric total electron content (TEC) and density altitude/latitude structure at mid and sub-auroral latitudes as a function of solar cycle, season, and level of geomagnetic activity. Existing observations taken over two solar cycles with the Millstone Hill incoherent scatter radar and available in the on-line Millstone Hill database will be the principal data set investigated.
Communications and navigation systems relying on trans-ionospheric propagation must be able to compensate for the effects of changing ionospheric characteristics over a wide range of temporal and spatial scales. Sharp changes in total electron content (TEC) are observed associated with the ionospheric density trough at mid latitudes over the northeastern US. An accurate characterization of these gradients and their variability is needed in the design and evaluation of navigation systems utilizing trans-ionospheric propagation in this regime.
