Solar-Activity Indices in the 24th Cycle and the Behavior of the Ionospheric F2-Layer

• Published in: Geomagnetism and Aeronomy Vol. 61; no. 2; pp. 222 - 226
• Main Author: Danilov, A. D.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.03.2021; Springer Nature B.V
• Subjects: Atmospheric correction; Earth and Environmental Science; Earth Sciences; F 2 region; foF2; Geophysics/Geodesy; Ionospheric layers; Solar activity; Trends; Ultraviolet radiation; Upper atmosphere
• ISSN: 0016-7932; 1555-645X; 0016-7940
• DOI: 10.1134/S0016793221020043

— This work is a continuation of the author’s earlier analysis of the relationship between the most often used solar-activity index, F 10.7, 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 F 10.7 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 F 10.7 values in the 24th cycle are lower than those in the two previous cycles. This explains the earlier finding that the use of the F 10.7 index without correction in the analysis of foF 2 and hmF 2 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 F 10.7 with the three aforementioned indices is proposed for the calculation of ionospheric trends.