Abstract The analysis of the behavior of the critical frequency foF2 during the 24th solar activity cycle (Danilov and Konstantinova, 2020a, c) is prolonged for two more months and the nighttime hours. In addition to the Rz and Ly-α indices used in the aforementioned papers for correction of the F10.7 index during the 24th cycle, the commonly used Mg II index is added. The results confirm the previous conclusions on the existence of the “vague” period with chaotic behavior of foF2 and the recovery of the negative trend in foF2 after 2008–2010. A comparison of the F10.7 index with three other SA indices (Ly-α, Rz, and Mg II) for the 22nd, 23rd, and 24th SA cycles is performed. It is shown that the relationship between F10.7 and other indices is close in the 22nd and 23rd cycles but differs from that in the 24th cycle. The corrected values of F10.7 in the 24th cycle are proposed for analysis of ionospheric trends during that cycle.

中文翻译：

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第 24 周期 F2 层参数和太阳活动指数的行为

摘要 对第 24 个太阳活动周期 (Danilov and Konstantinova, 2020a, c) 的临界频率 foF2 行为的分析延长了两个月以上的夜间时间。除了上述论文中用于修正第 24 周期 F10.7 指数的 Rz 和 Ly-α 指数外，还增加了常用的 Mg II 指数。结果证实了之前关于 foF2 存在混沌行为的“模糊”期和 2008-2010 年之后 foF2 负趋势恢复的结论。对第 22、23 和 24 次 SA 循环的 F10.7 指数与其他三个 SA 指数（Ly-α、Rz 和 Mg II）进行了比较。结果表明，F10.7 与其他指标的关系在第 22 和 23 周期接近，但与第 24 周期不同。F10 的修正值。