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Abstract:
Lastovicka (2021, 2023) found some differences in the dependence of yearly values foF2 on solar activity when different solar activity proxies were used. He used F10.7, F30, Mg II, solar H Lyman-α flux, sunspot numbers and He II. F30 followed by Mg II were established to be the optimum solar activity proxies, not traditionally used F10.7 and sunspot numbers, for yearly values of foF2. Here we use data of six ionospheric stations from four continents, Juliusruh, Pruhonice, Roma, Boulder, Kokubunji and Canberra, which reveal somewhat and sometimes even substantially different trends of foF2 when the effect of solar cycle is removed/reduced from foF2 data with different solar activity proxies.
