Global Ionospheric Models, TEC, and Stochastic Structure

Global Ionospheric Models (GIMs) provide parametric functional descriptions of ionospheric observables. Total electron content (TEC) is the primary propagation diagnostic. TEC is a measure of the cumulative interaction of an electromagnetic wave with the ionosphere, formally a path integral of electron density. The modeling challenge is determining the ionization distribution along the propagation path. Propagation effects can be exploited, but more often they complicate the inversion process. Although GIMs provide a repository of our understanding of ionospheric dynamics and a starting point for studying the development of stochastic structure, a viable stochastic component has yet to be incorporated. This talk will review some newly published results that connect configuration-space stochastic structure models directly to diagnostic measurements. The term scintillation, which is a frequency-dependent manifestation of ionospheric structure, has been avoided deliberately. The scintillation phenomenon is sufficiently well understood that progress is limited mainly by the lack of a unified structure model.