Comparison of the main ionospheric characteristics measured by the digisonde at Irkutsk in 2003 with IRI 2001 model data

Ionospheric characteristics derived from one year of ionograms recorded by a recently installed digisonde at Irkutsk, Russia (52.5N, 104.3E) are compared with the IRI-2001 model predictions. We tested alternative ways of solar activity specification in IRI to improve its prediction quality. In addition to the standard technique of using 12 monthly average sunspot numbers, R12, we also used monthly average and daily noon Rz and F10.7 index values available at the World Data Centers and elsewhere. Comparison of model to observations for monthly medians of major ionospheric characteristics and day-to-day variations of mean daily foF2 values is discussed.