Seasonal changes in the amplitude and phase of diurnal and semidiurnal variations in parameters of the midlatitude F2 layer under minimum solar activity conditions according to the data of an ionospheric station in Irkutsk (52.5°N, 104.0°E)

We performed a statistical and spectral analysis of variations in two main parameters of the ionospheric F2 layer: critical frequency (f (0)F2) and peak height (h (m) F2), recorded at an ionospheric station in Irkutsk (52.5A degrees N, 104.0A degrees E) in the period from December 1, 2006, to January 31, 2008, under low solar activity conditions. It was found that the f (0)F2 and h (m) F2 variations contained quasi-harmonic oscillations with periods T (n) = 24/n h (n = 1-7). We studied the seasonal changes in the mean and median values of monthly f (0)F2 and h (m) F2 time series, their spectra, as well as the amplitudes and phases of the diurnal (n = 1) and semidiurnal (n = 2) variations. It is shown that the amplitude of the diurnal f (0)F2 variations was maximal in October-March 2007 and minimal in May-August 2007. The diurnal f (0)F2 variations were maximal at noon in the winter months and at 1600 LT in the summer months. The semidiurnal f (0)F2 variations had two maxima: a primary maximum in December and January and a secondary maximum in May-July. The maxima of semidiurnal f (0)F2 variations were shifted from 0000 and 1200 LT in winter to 0900 and 2100 LT in summer.