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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 15, issue 8
Ann. Geophys., 15, 1015-1027, 1997
https://doi.org/10.1007/s00585-997-1015-0
© European Geosciences Union 1997
Ann. Geophys., 15, 1015-1027, 1997
https://doi.org/10.1007/s00585-997-1015-0
© European Geosciences Union 1997

  31 Aug 1997

31 Aug 1997

A 22-year cycle in the F layer ionization of the ionosphere

E. Feichter and R. Leitinger E. Feichter and R. Leitinger
  • Institut für Meteorologie und Geophysik, Universität Graz, Halbärthgasse 1, A-8010 Graz, Austria Tel: +43 316 380 5257; Fax: +43 316 384091;
    e-mail: leitinger@bkfung.kfunigraz.ac.at

Abstract. The double-sunspot-cycle variation in terrestrial magnetic activity has been well known for about 30 years. In 1990 we examined and compared the low-solar-activity (LSA) part of two consecutive cycles and predicted from this database and from published results the existence of a double-sunspot-cycle variation in total electron content (TEC) of the ionosphere too. This is restricted to noontime when the semi-annual component is well developed. Since 1995 we have had enough data for the statistical processing for high-solar-activity (HSA) conditions of two successive solar cycles. The results confirm the LSA findings. The annual variation of TEC shows a change from an autumn maximum in cycle 21 to a spring maximum during the next solar cycle. Similar to the aa indices for geomagnetic activity the TEC data show a phase change in the 1-year component of the Fourier transform of the annual variation. Additionally we found the same behaviour in the F-layer peak electron density (Nmax) over four solar cycles. This indicates that there exists a double-sunspot-cycle variation in the F-layer ionization over Europe too. It is very likely coupled with the 22-year cycle in geomagnetic activity.

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