Empirical orthogonal function analysis and modeling of the topside ionospheric and plasmaspheric TECs

Gridded TEC maps are first obtained from the original quiet time TECs, and then, they are decomposed into EOF basis modes and associated amplitude coefficients.

The EOF analysis well captures the latitudinal, longitudinal, and seasonal variations of the topside ionosphere and plasmasphere, and the associated dependence on solar EUV forcing. The first five EOFs, which can account for more than 98.8% of the total variance, are applied in model construction. The comparison with two empirical models indicates that the EOF TEC models can reproduce the observations well, including TEC magnitudes and longitudinal variations.