Temporal and spatial variations of global ionospheric total electron content under various solar conditions

摘要: By utilizing the numerical technique of principal component analysis (PCA), this work analyses temporal and spatial variations ionosphere under various solar conditions during period 1999–2013. Applying PCA to time series global ionospheric total electron content (TEC) maps provides an efficient method for analyzing main variability on a scale that is able decompose periodic (e.g., annual semiannual oscillations) while retaining asymmetry in domains seasonal equator anomalies). The TEC different local times are processed separately at two scales: (1) whole 15 years study (2) individual years. In contrast with previous studies, dataset 15 years shows dawn LT4–6) late morning (LT10–12) more remarkable characteristic variability. This also reveals cyclic trend respect times. first modes, which contain 80–90% variance, represent distributions stages cycle Annual demodulated from results show these evidently have distinct trends daytime nighttime. An exception that, active conditions, extremely strong irradiance has residual effect