Journal cover Journal topic
Annales Geophysicae An open-access journal of the European Geosciences Union
Ann. Geophys., 34, 1109-1117, 2016
http://www.ann-geophys.net/34/1109/2016/
doi:10.5194/angeo-34-1109-2016
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Regular paper
29 Nov 2016
Spatial and temporal variation of total electron content as revealed by principal component analysis
Elsayed R. Talaat1,a and Xun Zhu1 1The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, USA
anow at: Heliophysics Division, NASA Headquarters, Washington, D.C. 20546, USA
Abstract. Eleven years of global total electron content (TEC) data derived from the assimilated thermosphere–ionosphere electrodynamics general circulation model are analyzed using empirical orthogonal function (EOF) decomposition and the corresponding principal component analysis (PCA) technique. For the daily averaged TEC field, the first EOF explains more than 89 % and the first four EOFs explain more than 98 % of the total variance of the TEC field, indicating an effective data compression and clear separation of different physical processes. The effectiveness of the PCA technique for TEC is nearly insensitive to the horizontal resolution and the length of the data records. When the PCA is applied to global TEC including local-time variations, the rich spatial and temporal variations of field can be represented by the first three EOFs that explain 88 % of the total variance. The spectral analysis of the time series of the EOF coefficients reveals how different mechanisms such as solar flux variation, change in the orbital declination, nonlinear mode coupling and geomagnetic activity are separated and expressed in different EOFs. This work demonstrates the usefulness of using the PCA technique to assimilate and monitor the global TEC field.

Citation: Talaat, E. R. and Zhu, X.: Spatial and temporal variation of total electron content as revealed by principal component analysis, Ann. Geophys., 34, 1109-1117, doi:10.5194/angeo-34-1109-2016, 2016.
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Short summary
Global total electron content data derived from the assimilated thermosphere–ionosphere model are analyzed using empirical orthogonal function (EOF) decomposition and the principal component analysis technique. The spectral analysis of the time series of the EOF coefficients reveals how different mechanisms such as solar flux variation, change in the orbital declination, nonlinear mode coupling and geomagnetic activity are separated and expressed in different EOFs.
Global total electron content data derived from the assimilated thermosphere–ionosphere model...
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