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Ann. Geophys., 26, 335-344, 2008
www.ann-geophys.net/26/335/2008/
© European Geosciences Union 2008

Global electron content: a new conception to track solar activity

E. L. Afraimovich¹, E. I. Astafyeva¹, A. V. Oinats¹, Yu. V. Yasukevich¹, and I. V. Zhivetiev^2
1Institute Solar-Terrestrial Physics SB RAS, Irkutsk, Russia
²Institute of Cosmophysical Research and Radiowave Propagation, FEB RAS, Petropavlovsk-Kamchatskii, Russia

Abstract. We developed a method and programs for estimation of the global electron content (GEC) from GPS measurements, using the ionosphere models IRI-2001 and NeQuick. During the 23rd cycle of solar activity, the value of GEC varied from 0.8 to 3.2×10³² electrons, following changes in the solar extreme ultra violet (EUV) radiation and solar radio emission at 10.7-cm wavelength. We found a strong resemblance of these variations, with discernible 11-year and 27-day periodicities. A saturation effect of GEC is found when F10.7 increases. We found that GEC is characterized by strong seasonal (semiannual) variations with maximum relative amplitude at about 10% during the rising and falling parts of the solar activity and up to 30% during the period of maximum. It was found that the relative difference between model and experimental GEC series increase as the smoothing time window decreases. We found that GEC-IRI seasonal variations are out-of-phase with experimental GEC values. The lag between model and experimental maximum of GEC values can reach several tens of days. The variations of GEC lag, on average, 2 days after those of F10.7 and UV. GEC completely reflects the dynamics of the active regions on the solar surface. The amplitude of the 27-day GEC variations decreases from 8% at the rising and falling solar activity to 2% at the maximum and at the minimum. We also found that the lifetime of contrast long-living active formations on the Sun's surface in EUV range for more than 1 month exceeds the one in radio range (10.7 cm).

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Citation: Afraimovich, E. L., Astafyeva, E. I., Oinats, A. V., Yasukevich, Yu. V., and Zhivetiev, I. V.: Global electron content: a new conception to track solar activity, Ann. Geophys., 26, 335-344, 2008.   Bibtex   EndNote   Reference Manager