Abstract

The behavior of the critical frequency of the F2 layer, foF 2, during the 3 days preceding a magnetic storm is analyzed. A total of 254 storms in 1976–2010 were considered, and 1353 events (deviations of foF2 from quiet conditions) were found: 996 and 357 deviations had a positive and negative signs, respectively. It is found that the indicated deviations demonstrate a clearly pronounced and statistically significant dependence on the magnetic storm intensity (the minimal value of the Dst index), on the solar activity level (the F10.7 index), and on the season. The probability of the occurrence of the indicated deviations has clearly pronounced maxima 4–6, 12–13, and 18–20 h prior to the moment of the storm onset (SO). Moreover, the occurrence of the indicated deviations is most probable when the SO moment occurs at 0800–1000 and 1900–2100 LT. The results indicate that the found deviations are not occasional fluctuations in foF2 (Q disturbances) but are related to the subsequent magnetic storm, i.e., they are its precursors.

中文翻译：

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电磁风暴的电离层前兆。2.泥沼站数据分析

摘要

 分析了磁暴前三天F 2层的临界频率foF 2的行为。1976年至2010年，总共考虑了254次风暴，发现了1353个事件（foF 2与安静条件的偏离）：996个和357个偏差分别具有正号和负号。发现所指示的偏差表明对磁暴强度（Dst指数的最小值），太阳活动水平（F10.7索引），并按季节显示。出现指示偏差的可能性已在风暴开始（SO）之前的4–6、12–13和18–20 h明显达到最大值。此外，当SO矩出现在0800–1000和1900–2100 LT时，最有可能出现指示的偏差。结果表明，发现的偏差不是foF 2的偶然波动（Q扰动），而是与随后的磁暴有关，即它们是其前兆。