Abstract

Ionosonde measurements of the critical frequency of the ionospheric F2 layer (foF2) at Wakkanai station (Japan) are analyzed with the method of superposed epochs. The station is situated in a region of high seismicity. Winter periods with low sunspot and geomagnetic activity and high seismic activity are considered. The goals of this work were the quantitative characterization and comparison of ionospheric disturbances induced by the development of geomagnetic storms/geomagnetic disturbances. Geomagnetic disturbances refer to manifestations of geomagnetic activity with an intensity that is higher than “quiet” geomagnetic background but not higher than the threshold characteristic of weak geomagnetic storms. It is ascertained that weak geomagnetic storms and geomagnetic disturbances, from the time of the main trough in the Dst index after the onset of a geomagnetic storm/geomagnetic disturbance to the end of the third day, result in only positive foF2 deviations. The deviations exceed 6% of the background; the maximal relative deviations from the background (δfoF2_max) are ~17% and ~14%, respectively. For geomagnetic disturbances, the most significant response of the ionosphere is observed ~7 h after the main trough in the Dst index. The resulting assessments can be used to filter out false ionospheric earthquake precursors with analysis of the ionospheric data from Wakkanai station.

中文翻译：

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基于稚内站的数据估算地磁干扰的电离层效应

摘要

电离层F 2层临界频率（foF2）在日本稚内站采用叠加时代法进行分析。气象站位于地震活动频繁的地区。考虑低太阳黑子，地磁活动和高地震活动的冬季。这项工作的目的是定量描述和比较由地磁风暴/地磁干扰的发展引起的电离层干扰。地磁干扰是指强度高于“安静”地磁背景但不高于弱地磁风暴的阈值特征的地磁活动表现。从Dst的主要槽期开始，可以确定地磁风暴和地磁干扰较弱地磁风暴/地磁扰动发生后至第三天结束时的指数，只会导致foF 2正偏差。偏差超过背景值的6％；与背景的最大相对偏差（δfoF 2 _max）分别为〜17％和〜14％。对于地磁干扰，在Dst指数的主要波谷后约7小时，观察到电离层的最显着响应。通过对稚内站电离层数据的分析，所得评估结果可用于滤除假的电离层地震前兆。