Özet:

This paper presents the critical frequency foF2 behavior using in situ data and predicted one with IRI-2012 subroutines CCR and URSI during the solar cycles 21 and 22 under shocks conditions. Our investigations allowed us to identify the five types of profiles according to Faynot and Villa (1979) and observed important characteristics about foF2 amplitude seasonal variation during each solar cycle phase. The amplitudes of each type of profile depend on solar cycle phase and season. Lowest amplitudes are recorded during summer for all phases and seasons. The highest amplitude and observed during winter/ autumn for all the solar cycle phases except for solar minimum phase where maximum is observed on spring. A gap in the amplitude is observed most of the time between in situ measured data and IRI predictions. Concordance between measured data profiles and predictions is about 42. 85% with CCIR and 64. 28% with URSI. The different profiles obtained are characteristics of the presence or absence of electrojet phenomenon during morning or afternoon as reviewed by Vassal and al. (1982).

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