Trends in the ionospheric E and F regions over Europe

Abstract. Continuous observations in the ionospheric E and F regions have been regularly carried out since the fifties of this century at many ionosonde stations. Using these data from 31 European stations long-term trends have been derived for different parameters of the ionospheric E layer (h' E, foE), F1 layer (foF1) and F2 layer (hmF2, foF2). The detected trends in the E and F1 layers (lowering of the E region height h'E; increase of the peak electron densities of the E and F1 layers, foE and foF1) are in qualitative agreement with model predictions of an increasing atmospheric greenhouse effect. In the F2 region, however, the results are more complex. Whereas in the European region west of 30° E negative trends in hmF2 (peak height of the F2 layer) and in the peak electron density (foF2) have been found, in the eastern part of Europe (east of 30° E) positive trends dominate in both parameters. These marked longitudinal differences cannot be explained by an increasing greenhouse effect only, here probably dynamical effects in the F2 layer seem to play an essential role.

Key words. Atmospheric composition and structure (Pressure · density and temperature) · Ionosphere (Mid-latitude ionosphere) · Radio science (Ionospheric propagation).