Kassa Yibekal, Tebabal Ambelu, Damtie Baylie
College of Science, Department of Physics, Washera Geospace and Radar Science Research Laboratory (WaGRL), Bahir Dar University, Ethiopia.
College of Natural and Computational Science, Department of Physics, Debre Markos University, Ethiopia.
Heliyon. 2024 Sep 23;10(19):e38138. doi: 10.1016/j.heliyon.2024.e38138. eCollection 2024 Oct 15.
Radio communication and navigation systems can be severely impacted by irregularities in the ionosphere. There is still much to learn about how geomagnetic storms affect the occurrence of these irregularities. Ionosphere studies in different regions, particularly the equatorial and low-latitudes, are necessary to enhance the forecasting of this phenomenon. This study investigates the effect of intense geomagnetic storm events of August 27, October 7 and December 22, 2015, on nighttime ionospheric irregularities. Data collected from the receivers of the Global Navigation Satellite Systems (GNSS) in specific longitudinal sector of 15W - 0, 0 - 15E, 15E - 30E and 30E - 45E, as well as from the Swarm constellations in the longitude range of W - E and the latitude range of S - N, have been used. The rate of change of the total electron content (TEC) index (ROTI) and the rate of change of the electron density index (RODI) were analyzed. In the main phases of the storms, at equatorial and low-latitude regions we observed ionospheric irregularities in the African longitudinal sectors of 15W - 0, 0 - 15E and 30E - 45E in the three storm events. The observed ionospheric irregularities were more pronounced in the western than eastern regions. These irregularities were possibly driven by the Prompt Penetration Electric Fields (PPEFs) that point east to west during nighttime. Ionospheric irregularities were inhibited in the selected storm periods over the middle latitudes in the African sector. In the longitudinal sector of 15E - 30E, we obtained inhibition of irregularity in the study periods. In the case of the top-side ionosphere, we observed enhanced and depleted electron density during the storm in the low latitude and equatorial regions. In the low latitude and equatorial regions, there were electron density fluctuations within the range of N and S, indicating significant top-side irregularities.
无线电通信和导航系统可能会受到电离层不规则现象的严重影响。关于地磁风暴如何影响这些不规则现象的发生，仍有许多需要了解的地方。对不同区域，特别是赤道和低纬度地区进行电离层研究，对于加强对这一现象的预测是必要的。本研究调查了2015年8月27日、10月7日和12月22日的强烈地磁风暴事件对夜间电离层不规则现象的影响。使用了从全球导航卫星系统（GNSS）接收机在15W - 0、0 - 15E、15E - 30E和30E - 45E的特定纵向扇区收集的数据，以及从“蜂群”星座在W - E经度范围和S - N纬度范围内收集的数据。分析了总电子含量（TEC）指数的变化率（ROTI）和电子密度指数的变化率（RODI）。在风暴的主要阶段，在赤道和低纬度地区，我们在这三次风暴事件中观测到非洲纵向扇区15W - 0、0 - 15E和30E - 45E存在电离层不规则现象。观测到的电离层不规则现象在西部地区比东部地区更为明显。这些不规则现象可能是由夜间从东向西的迅速穿透电场（PPEFs）驱动的。在非洲扇区的中纬度地区，在选定的风暴期间电离层不规则现象受到抑制。在15E - 30E纵向扇区，我们在研究期间获得了不规则现象的抑制情况。在电离层顶侧的情况下，我们在低纬度和赤道地区的风暴期间观测到电子密度增强和减少。在低纬度和赤道地区，存在N和S范围内的电子密度波动，表明电离层顶侧存在明显的不规则现象。
