A SINGLE-STATION SPECTRAL MODEL OF THE MONTHLY MEDIAN FOF2 AND M(3000)F2

A new single-station model (SSM) for monthly median values of the iono spheric parameters foF2 and M (3000)F2 has been developed. Fourier ana lysis provides a tool for decomposing the time-varying ionospheric par ameters. The 12-month smoothed sunspot number R-12 was used as an exte rnal solar characteristic because of its availability and predictabili ty. However, for the first time, the solar activity is described not o nly by R-12, but also by the linear coefficient K-R representing the t endency of the change of solar activity. A general non-linear approxim ation of the influence of the solar-cycle characteristics R-12 and K-R and ionospheric parameters foF2 and M(3000)F2 was accepted. The new S SM is applied to several European stations and its statistical evaluat ion shows better results tan the other two SSMs used in the paper. The approach described in the paper does not contradict the use of differ ent synthetic ionospheric indices (as the T-index, MF2-index); the bas ic aim is to show only that using one additional new characteristic of the solar-cycle variations, such as K-R, improves the monthly median model.