Abstract

A solar eclipse (SE) causes recordable disturbances in all subsystems of the Earth–atmosphere–ionosphere–magnetosphere system and in geophysical fields. The response of the system to an SE substantially depends on the eclipse magnitude, the solar cycle phase, the atmospheric and space weather, the season, the time, and the observation coordinates. Manifestations of the response are also influenced by the observation technique. Despite the fact that the effect of a solar eclipse on the ionosphere has been studied for approximately 100 years, a number of unresolved issues remain. The purpose of this study is to describe the results of our analysis of temporal total electron content (TEC) variations caused by the annular solar eclipse on June 21, 2020, in the equatorial ionosphere. The authors analyzed 132 time dependences of the TEC that covered an extensive region with an eclipse. The maximum magnitude (M_max = 0.9940) of the eclipse, which began at 06:39:59 UT, was observed in northern India in Uttarakhand and lasted 38 s. Space weather conditions on June 21, 2020, were favorable for studying the effects associated with the SE. To reveal the response of the ionosphere to the annular SE on June 21, 2020, the GPS signal recordings were processed. Time variations of the TEC in the ionosphere on reference days and on the SE day of June 21, 2020, were analyzed on a global scale. For this purpose, the results of measurements at twelve stations and eleven GPS satellites were used. The dependences of the absolute and relative TEC value decreases caused by the SE on a time of day are studied. The lowest value of the TEC decrease (–2…–3 TECU) was observed in the morning. In the daytime and in the evening hours, it reached –4…–6 TECU. The relative decrease in the TEC barely depended on a time of day and reached –30…–35%. No stable dependence of the TEC decrease on the eclipse magnitude was found. The relative value of the TEC decrease depended on the SE magnitude, i.e., smaller values of the SE magnitude corresponded to smaller values of the relative TEC decrease. The duration of the TEC reduction exceeded the duration of the eclipse by 1.5–2.5 h. The time of reaching the minimum TEC values in the daytime and the evening hours delayed by 10–20 min with respect to the time of reaching the maximum SE magnitude. Wave-like disturbances of the TEC were practically absent. Undisturbed TEC values and the TEC values disturbed by the eclipse substantially depended on the location of stations and the trajectory of satellites, which was associated with the influence of equatorial ionization anomaly. This is the main peculiarity of ionospheric effects of the SE at latitudes 0°–30° N.

中文翻译：

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2020年6月21日日环食期间赤道电离层总电子含量的全球变化

摘要

日食（SE）会对地球-大气层-电离层-磁层系统的所有子系统和地球物理场造成可记录的扰动。系统对 SE 的响应很大程度上取决于日食星等、太阳周期相位、大气和太空天气、季节、时间和观测坐标。反应的表现也受到观察技术的影响。尽管人们对日食对电离层的影响的研究已经进行了大约 100 年，但仍有许多未解决的问题。本研究的目的是描述我们对 2020 年 6 月 21 日日环食在赤道电离层中引起的时间总电子含量 (TEC) 变化的分析结果。作者分析了 TEC 的 132 个时间依赖性，这些 TEC 覆盖了发生日食的广阔区域。最大震级（_最大米= 0.9940）的日食于世界标准时间 06:39:59 开始，在印度北部的北阿坎德邦观测到，持续了 38 秒。2020 年 6 月 21 日的太空天气条件有利于研究 SE 相关的影响。为了揭示 2020 年 6 月 21 日电离层对环形 SE 的响应，对 GPS 信号记录进行了处理。在全球范围内分析了参考日和 2020 年 6 月 21 日 SE 日电离层 TEC 的时间变化。为此，使用了 12 个站点和 11 颗 GPS 卫星的测量结果。研究了 SE 引起的绝对和相对 TEC 值降低对一天中某个时间的依赖性。TEC 下降的最低值 (–2…–3 TECU) 出现在早晨。白天和晚上，达到 –4…–6 TECU。TEC 的相对下降几乎不依赖于一天中的某个时间，达到 –30…–35%。没有发现 TEC 下降对日食星等的稳定依赖性。TEC降低的相对值取决于SE幅度，即SE幅度的较小值对应于相对TEC降低的较小值。TEC 减少的持续时间比日食的持续时间多了 1.5-2.5 小时。白天和晚上达到最小TEC值的时间比达到最大SE震级的时间延迟10~20分钟。TEC 的波状扰动实际上不存在。未受干扰的 TEC 值和受日食干扰的 TEC 值在很大程度上取决于站的位置和卫星的轨迹，这与赤道电离异常的影响有关。这是北纬 0°–30°SE 电离层效应的主要特点。