Abstract

Multiyear researches show that weak and moderate magnetic storms may induce considerable and unpredictable changes in the ionosphere state. The problems of predicting the ionosphere response in a certain region to space weather changes currently remain topical since the physical processes occurring in the ionospheric plasma are variable and complicated. Particular interest is attracted by ionospheric disturbances with variable phases at middle latitudes and their propagation to low latitudes and the occurrence of strong ionospheric storms as a result of moderate or weak magnetic storms. The objective of this study is to perform the experimental studies of variations in the ionospheric plasma parameters over Ukraine during the very moderate magnetic storm on December 18, 2019. The study was carried out by using the incoherent scatter of radio waves as providing the most complete diagnostic capabilities and the vertical sounding method. Observations were performed in the Ionospheric Observatory of the Institute of Ionosphere (National Academy of Sciences of Ukraine, Ministry of Education and Science of Ukraine, Kharkiv) with an incoherent scatter radar. The critical frequencies were measured with a portable ionosonde. In addition, the geophysical information about the space weather and magnetosphere parameters was used. The ionosphere response to the geospace storm on December 18, 2019, over Kharkiv was analyzed. The very moderate magnetic storm (K_p = 4) was established to induce positive ionospheric disturbance. An increase in the critical frequency (up to 1.6 times) and a corresponding increase in the ionospheric F2 peak electron density (up to 2.6 times) was accompanied by a sequence of changes in the variations of principal ionospheric plasma parameters, such as the F2 layer peak height (a decrease by 30 km), the electron density throughout the entire range of studied altitudes (200–450 km), the electron and ion temperatures, and the vertical ionospheric plasma velocity component (with a decrease in the downward plasma drift velocity V_z at the noon after the magnetic storm began with further velocity recovery, the occurrence of fluctuations in the variations V_z with a quasi-period of 1 h 50 min at 15:40 UT (Universal Time) at altitudes of 360–420 km, and weakening of the evening extremum effect in the V_z variations and a maximum decrease in the velocity to 40–70 m/s at these altitudes). A substantiation was given for the following mechanism of the formation of a positive ionospheric storm: the downward plasma drift is weakened in the mid-latitude ionosphere during the winter daylight due to the fact that normal circulation is weakened by reverse storm-induced circulation. The very moderate magnetic storm on December 18, 2019, induced appreciable changes in the ionospheric plasma parameters throughout the entire range of studied altitudes. The measured data provided additional information for solar-terrestrial relationships study and the ionosphere state prediction.

中文翻译：

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2019 年 12 月 18 日中等强度磁暴期间乌克兰上空中纬度电离层参数的变化

摘要

多年的研究表明，弱和中等磁暴可能会引起电离层状态发生相当大且不可预测的变化。由于电离层等离子体中发生的物理过程多变且复杂，因此预测特定区域的电离层对空间天气变化的响应问题目前仍然是热门话题。特别感兴趣的是在中纬度具有可变相位的电离层扰动及其向低纬度的传播以及由于中等或弱磁暴而发生的强电离层风暴。本研究的目的是对 2019 年 12 月 18 日中等强度磁暴期间乌克兰上空电离层等离子体参数变化进行实验研究。该研究是通过使用无线电波的非相干散射作为提供最完整的诊断能力和垂直探测方法进行的。观测是在电离层研究所的电离层天文台（乌克兰国家科学院，乌克兰教育和科学部，哈尔科夫）使用非相干散射雷达进行的。临界频率是用便携式离子探空仪测量的。此外，还使用了有关空间天气和磁层参数的地球物理信息。分析了 2019 年 12 月 18 日哈尔科夫上空的地球空间风暴对电离层的响应。非常温和的磁暴（观测是在电离层研究所的电离层天文台（乌克兰国家科学院，乌克兰教育和科学部，哈尔科夫）使用非相干散射雷达进行的。临界频率是用便携式离子探空仪测量的。此外，还使用了有关空间天气和磁层参数的地球物理信息。分析了 2019 年 12 月 18 日哈尔科夫上空的地球空间风暴对电离层的响应。非常温和的磁暴（观测是在电离层研究所的电离层天文台（乌克兰国家科学院，乌克兰教育和科学部，哈尔科夫）使用非相干散射雷达进行的。临界频率是用便携式离子探空仪测量的。此外，还使用了有关空间天气和磁层参数的地球物理信息。分析了 2019 年 12 月 18 日哈尔科夫上空的地球空间风暴对电离层的响应。非常温和的磁暴（分析了 2019 年 12 月 18 日哈尔科夫上空的地球空间风暴对电离层的响应。非常温和的磁暴（分析了 2019 年 12 月 18 日哈尔科夫上空的地球空间风暴对电离层的响应。非常温和的磁暴（K _p = 4) 的建立是为了诱导正电离层干扰。临界频率的增加（高达 1.6 倍）和电离层F 2 峰值电子密度的相应增加（高达 2.6 倍）伴随着主要电离层等离子体参数变化的一系列变化，例如F 2 层峰高（减少 30 公里），整个研究高度范围内的电子密度（200-450 公里），电子和离子温度，以及垂直电离层等离子体速度分量（向下等离子体减少磁暴开始后中午的漂移速度V _{z进一步恢复速度，变化出现波动}V _z在 15:40 UT（世界时间）准周期为 1 小时 50 分钟，高度为 360–420 km，V z_{中的夜间极值效应减弱}在这些高度变化和最大速度下降到 40–70 m/s）。给出了正电离层风暴形成机制的佐证：冬季白天中纬度电离层等离子体向下漂移减弱，这是由于正常环流被逆风暴引起的环流减弱所致。2019 年 12 月 18 日发生的中等强度磁暴在整个研究高度范围内引起了电离层等离子体参数的明显变化。测量数据为日地关系研究和电离层状态预测提供了额外的信息。