In the study the critical frequency of the F2-layer of the ionosphere data obtained at Ionospheric Observatory of Tomsk State University are analyzed. The analysis focuses on the study of the spectral composition and determining the longterm trends values of foF2. For the spectral estimation the anharmonic decomposition method is used. The result of research is establishing the dependence of a long-period trends character, periods values and the amplitudes of variations of foF2 values caused by the eleven-year cycle of the Sun activity and orbital movement of the Earth on time of a day and a season of year.Keywords: critical frequency of the ionospheric plasma, spectral analysis, a trend, seasonal and daily variations.

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This study is devoted to the development of new techniques for the research of the ionosphere state. This paper describes the new approaches to development and implementation of the methods for remote radio sounding of the ionosphere on the basis of the world technological advances and the most innovative methods of data analysis, applied at Ionospheric Observatory of Tomsk State University using data processing software Dynasonde 21.Keywords: monitoring of the Earth's ionosphere, a method of vertical radio sounding of the ionosphere, a digital ionosonde.

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