Dependence of the resonant electromagnetic background frequencies in the frequency range of the alfven ionospheric resonator on the level of the solar activity

In the work, variations of the resonant electromagnetic background frequencies in the frequency range of the ionospheric Alfven resonator are investigated. An algorithm of automatic determination of the resonant characteristics of registered signals is presented. It is established that the variations of the resonant frequencies are determined on 75% by their seasonal changes; the relative contribution of the 11-year period caused by the solar activity does not exceed 15%.