A wavelet analysis of F2 layer critical frequency over solar cycle 23

摘要

Temporal oscillations of F2 layer critical frequency are direct outcome of solar EUV variability. The hourly data of F2 layer critical frequency (f_oF_2) during solar cycle 23 over eight ionosonde stations which falls within same longitudinal span are evaluated using Continuous Wavelet Transform (CWT) to estimate the ionospheric variations. The quasi triennial, annual, semiannual, 27 day and diurnal variations of f_oF_2 are clearly evident in the wavelet power spectra of all the stations. Quasi triennial oscillations which show a clear latitudinal dependence is more evident in southern stations. A strong quasi biennial oscillation (QBO) is also noticed in higher latitudes which was not observable in equatorial latitude. The present study reveals that the semiannual variations are more obvious over the annual variation in the equatorial and low latitude stations while the annual variations are prominent in higher latitudes.