Ionospheric equivalent slab thickness and its modeling applications

A data base of equivalent slab thickness observations covering nearly two complete solar cycles has been obtained at a mid‐latitude site (Hamilton, Massachusetts). The mean variations are described both qualitatively, in terms of changes to profile shapes, and quantitatively, in terms of a simple numerical model. A number of currently available ionospheric models have also been used to predict values of slab thickness (τ = total electron content/ N max ) over Hamilton, Massachusetts, and comparisons of these values with those observed provided validation of the models. Adjustments to the model profiles were suggested in a couple of cases.