Abstract

The F2-layer critical frequency foF2 is analyzed for three days preceding a magnetic storm based on Juliusruh station data. A total of 272 storms over the period 1976–2010 are considered, and 2682 events (foF2 deviations from quiet conditions) are found. There were 2007 deviations with positive signs and 675 deviations with negative signs. It was found that the aforementioned deviations demonstrate a well-pronounced and statistically significant dependence on the magnetic-storm intensity (the minimal value of the Dst index), the solar-activity level (the F10.7 index), and the season. The highest probability of the occurrence of the indicated deviations is observed 4–12 and 22–23 h prior to the moment of storm onset (SO). Moreover, the occurrence of these deviations is most probable when the SO moment occurs at 0400, 0700–0800, 1200–1300, and 2200 LT. The results agree well with authors’ previously published results with the Slough data and indicate that the discovered deviations are not casual foF2 fluctuations (Q disturbances) but are related to the coming magnetic storm, i.e., they are its precursors.

中文翻译：

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磁暴的电离层前兆。3. Juliusruh 站数据分析

摘要

根据 Juliusruh 台站数据，对磁暴前三天的F 2 层临界频率foF 2 进行了分析。总共考虑了 1976-2010 年期间的 272 场风暴，发现了 2682 次事件（与安静条件的foF 2 偏差）。2007 年有正号偏差，675 次偏差有负号。发现上述偏差表明对磁暴强度（Dst指数的最小值）、太阳活动水平（F10.7 指数）和季节。出现指示偏差的最高概率是在风暴开始 (SO) 前 4-12 小时和 22-23 小时观察到的。此外，当 SO 时刻发生在 0400、0700-0800、1200-1300 和 2200 LT 时，这些偏差最有可能发生。结果与作者之前发表的斯劳数据结果非常吻合，并表明发现的偏差不是偶然的foF 2 波动（Q 扰动），而是与即将到来的磁暴有关，即它们是其前兆。