Statistical characteristics of the total ion density in the topside ionosphere during the period 1996-2004 using empirical orthogonal function (EOF) analysis

Abstract

Abstract.We have applied the empirical orthogonal function (EOF) analysis to examine the climatology of the total ion density Ni at 840 km during the period 1996-2004, obtained from the Defense Meteorological Satellite Program (DMSP) spacecraft. The data set for each of the local time (09:30 LT and 21:30 LT) is decomposed into a time mean plus the sum of EOF bases E i of space, multiplied by time-varying EOF coefficients A i . Physical explanations are made on the first three EOFs, which together can capture more than 95% of the total variance of the original data set. Results show that the dominant mode that controls the N i variability is the solar EUV flux, which is consistent with the results of Rich et al. (2003). The second EOF, associated with the solar declination, presents an annual (summer to winter) asymmetry that is caused by the transequatorial winds. The semiannual variation that appears in the third EOF for the evening sector is interpreted as both the effects of the equatorial electric fields and the wind patterns. Both the annual and semiannual variations are modulated by the solar flux, which has a close relationship with the O + composition. The quick convergence of the EOF expansion makes it very convenient to construct an empirical model for the original data set. The modeled results show that the accuracy of the prediction depends mainly on the first principal component which has a close relationship with the solar EUV flux.

Features of annual and semiannual variations derived from the global ionospheric maps of total electron content

“…Observational evidence indicates that there is no winter anomaly in the topside ionosphere, whereas it is significant in the F-region (e.g. Balan et al, 1998;Torr and Torr, 1973;Su et al, 1998;Zhao et al, 2005;Liu et al, 2007). Moreover, observational evidence also shows that the annual anomaly is very strong in the topside ionosphere, as compared with the bottomside ionosphere (Su et al, 1998).…”

Modeling ionospheric <I>fo</I>F2 by using empirical orthogonal function analysis

“…Dvinskikh (1988) first introduced EOF analysis into the empirical modeling of the ionospheric parameters. It has been confirmed by many researchers that EOF analysis is a powerful method for ionospheric modeling and data analysis (e.g., Singer and Dvinskikh, 1991;Daniell et al, 1995;Matsuo et al, 2002Matsuo et al, , 2005Marsh et al, 2004;Zhao et al, 2005;Zapfe et al, 2006;Liu et al, 2008;Mao et al, 2008;Zhang et al, 2009;Matsuo and Forbes, 2010, and more). According to EOF theory, the variation of the ionospheric parameters are attributed to different factors which can be extracted and separated in terms of their relative "contribution" with respect to ionospheric parameters.…”

Annual and semiannual variations of vertical total electron content during high solar activity based on GPS observations

“…Correspondence to: M. P. Natali (paula@fcaglp.unlp.edu.ar) F2-layer peak electron content (NmF2) and TEC (Rishbeth, 1998;Rishbeth et al, 2000;Zou et al, 2000;Liu et al, 2009;Zhao et al, 2005;Meza and Natali, 2008). These anomalies can be summarized as follows:…”