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

E. Feichter (1) , R. Leitinger (1)

1 Institut für Meteorologie und Geophysik [Graz]

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 (N_max) 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.

Domaines: Océan, Atmosphère; Sciences de la Terre

E. Feichter, R. Leitinger. A 22-year cycle in the F layer ionization of the ionosphere. Annales Geophysicae, 1997, 15 (8), pp.1015-1027. ⟨hal-00316305⟩