Letter to the Editor: Solar-cycle variation of the daily foF2 and M(3000)F2

Abstract. Daily values of the ionospheric characteristics foF2 and M(3000)F2 for a given hour and month are correlated with the corresponding daily values of sunspot number using measured data collected at seven European locations. The significance of applying different-order polynomials is considered and the times are confirmed when the higher-order terms are important. Mean correlation coefficients for combined data sets over all hours, months and stations are determined, together with the standard errors of estimates. Comparisons are made with corresponding figures for monthly median values derived from the same data sets.

Key words. Electromagnetics (Guided waves) · Ionosphere (Ionospheric disturbances) · Radio Science (Radio wave propagation)