Abstract :
Current state of the D-region modeling in the scope of the IRI is briefly discussed. The empirical models available account for the altitude, diurnal and regular seasonal variations of the [e] values at 60–90 km. However, there are clear indications to the existence of long-term variations (trends) of the electron concentration in the D region, which should be taken into account in empirical models. Some comparisons of the data for the Arctic and Antarctic stations are presented. The question of the D-region dependence on solar activity ·is briefly discussed. There are indications that the quasi-biennial oscillations may be involved into this dependence.
