Predicted and measured bottomside F-region electron density and variability of the D ₁ parameter under quiet and disturbed conditions over Europe

Modelling and forecasting of ionospheric parameters is very useful for different radio communication purposes. As long as variations in the ionosphere form regular patterns, the empirical International Reference Ionosphere model, IRI 2000, provides sufficiently accurate corrections to the maximum electron density, N _m F2, to predict the ionospheric effects on radio wave propagation. During geomagnetic storms, however, agreement between the IRI 2000 model and observations is still insufficient. This paper deals with the analysis of measured and model predicted F-region electron densities under quiet and disturbed conditions with the main emphasis placed on the distribution of the F1-region daytime ionisation. Available electron density profiles obtained from ionograms for selected periods from several European ionospheric stations (Pruhonice, Ebro, Arenosillo) were compared with IRI 2000 model results. Comparative analysis shows that discrepancies do exist predominantly during the storm main phase. The model predicted daytime electron densities at the fixed Fl-region heights are closer to observed values during summer than winter. Dependences of D ₁ on solar activity and season are also analysed.