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Empirical Orthogonal Function Analysis and Modeling of the Topside Ionospheric and Plasmaspheric TECs
Author(s) -
Zhong Jiahao,
Lei Jiuhou,
Yue Xinan,
Wang Wenbin,
Burns Alan G.,
Luan Xiaoli,
Dou Xiankang
Publication year - 2019
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1029/2019ja026691
Subject(s) - tec , empirical orthogonal functions , plasmasphere , ionosphere , international reference ionosphere , northern hemisphere , anomaly (physics) , atmospheric sciences , environmental science , middle latitudes , climatology , southern hemisphere , total electron content , forcing (mathematics) , geology , physics , geophysics , magnetosphere , plasma , quantum mechanics , condensed matter physics
Abstract The topside total electron contents (TECs) observed by the MetOp‐A (above 832 km) and TerraSAR‐X (above 520 km) satellites for multiple local times during 2008–2018 have been used to develop global topside ionospheric and plasmaspheric TEC models, based on empirical orthogonal function (EOF) analysis. 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. Moreover, the annual anomaly is obviously seen in the topside TECs. The global averaged TECs are greatest in December and smallest in June. With increasing solar EUV forcing, the global averaged TECs always increase, but the winter hemisphere TECs do not change much and even decrease, especially at night and in the Southern Hemisphere. The overall increasing rate with solar EUV forcing is larger under higher solar activity conditions. The direct plasma diffusion through ionosphere‐plasmasphere coupling may not be able to explain some of the features seen in the topside TECs.