Highlights Long-term trends in foF2 change remarkably with the solar activity proxy used. F30 is the only proxy, which provides trends of the same sign for all stations. I recommend F30 as the best solar proxy for trends of foF2 at midlatitudes.
Abstract The most studied ionospheric parameter for long-term trends is foF2. The dominant factor of foF2 variability is the solar cycle, which is much stronger than the long-term trends. Therefore its effect in data must be removed. However, several decade long homogeneous measurements of the solar EUV fluxes are not available, so various solar activity proxies (solar activity indices) must be used. The aim of this paper is to study the impact of selection of different solar activity proxies on foF2 long-term trends and to find the best solar activity proxy for foF2 trends at middle latitudes. The results based on yearly average data of six midlatitude stations from four continents (1976–2014) and of six solar activity proxies show that the long-term trends in foF2 depend substantially on the solar activity proxy used, and the only solar proxy, which provides trends of the same sign for all stations and both sub-periods, is F30. Based on results of this paper and that of , I can recommend F30 as the best solar proxy for studying long-term trends of foF2 at middle latitudes (at least for yearly average values).
Dependence of long-term trends in foF2 at middle latitudes on different solar activity proxies
Advances in Space Research ; 73 , 1 ; 685-689
2023-09-21
5 pages
Article (Journal)
Electronic Resource
English
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