Abstract—
This work is a continuation of the author’s earlier analysis of the relationship between the most often used solar-activity index, F10.7, and solar-activity indices (Ly-α, Rz and Mg II) that reflect variations of the ultraviolet radiation of the Sun, which governs the behavior of the main ionospheric layers. It is shown that the relationship between F10.7 and the three aforementioned indices are close to each other in the 22nd and 23rd activity cycles. However, they differ from those in the two previous cycles and are less statistically significant in the 24th cycle. For the same values of the Ly-α, Rz, and Mg II indices, the F10.7 values in the 24th cycle are lower than those in the two previous cycles. This explains the earlier finding that the use of the F10.7 index without correction in the analysis of foF2 and hmF2 behavior in the 24th cycle leads to positive trends, which contradicts the current ideas on the cooling and contraction of the upper atmosphere. Correction of the F10.7 with the three aforementioned indices is proposed for the calculation of ionospheric trends.
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The monthly mean values of the sunspot numbers Rz and the Ly-α and Mg II indices were taken from the site (https://lasp.colorado.edu).
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Translated by A. Danilov
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Danilov, A.D. Solar-Activity Indices in the 24th Cycle and the Behavior of the Ionospheric F2-Layer. Geomagn. Aeron. 61, 222–226 (2021). https://doi.org/10.1134/S0016793221020043
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DOI: https://doi.org/10.1134/S0016793221020043