Analysis of the ionospheric variability based on wavelet decomposition

In this work, the ionospheric variability is analyzed by applying the wavelet decomposition technique to the noontime foF2, F10.7, interplanetary magnetic field (IMF) Bz, Ap, and lower thermospheric temperature at pressure of 10−4 hPa in 2002. Results show that the variance of periodic oscillations in the ionosphere is largest in the 2–4-day period and declines with the increase of the period. The maximum variance of the periodic oscillations in solar irradiation is in the 16–32-day period. For geomagnetic activities, most of the variance is about equally distributed on intervals of periods shorter than 32 days. Variance distributions of IMF Bz and lower thermospheric temperature are similar to those of the ionosphere. They show the maximum in the 2–4-day period and decline with the increase of the period. By analyzing the distributions of the variances, the potential connections between the ionosphere and the external sources are discussed.