Global Ionospheric TEC and ROTI Variations during a Moderate Geomagnetic Storm
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摘要: 地磁暴发生时，电离层会有偏离平均水平的强烈扰动.基于全球电离层TEC及其时间变化率ROTI （Rate of TEC Index）数据，对2014年8月一次中等强度磁暴期间的全球电离层影响进行了分析，探讨了磁暴所引发电离层暴的可能机制.研究发现，本次磁暴伴随有明显的电离层暴效应.磁暴期间：南半球电离层以正相暴为主，北半球电离层暴则整体表现为短暂正相暴后长时间强的负相暴；电离层在北半球的下降比南半球强，并且这种下降持续了约一周时间；低纬区域电离层变化幅度明显小于中纬区域，高纬区域则主要表现为负暴效应；赤道北驼峰出现了明显的南移现象，直至磁赤道两侧双驼峰结构消失.对磁暴期间三个不同扇区的电离层ROTI变化的分析表明：欧洲—非洲扇区磁暴前有电离层闪烁发生，磁暴发生后消失，而东亚—澳大利亚及美洲扇区则无此现象出现.研究结果表明，此次磁暴期间的电离层变化存在明显的时间和空间差异.
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关键词:
- 地磁暴 /
- 电离层 /
- 总电子含量 /
- 总电子含量变化率指数
Abstract: The ionosphere will have strong disturbances on geomagnetic storm days. The physical mechanism causing an ionospheric disturbance is very complex, various dynamics and electrodynamics processes in magnetosphere/thermosphere lead to great differences in ionospheric morphology and response in different locations and different time during a geomagnetic storm. Therefore, the geomagnetic storm has always been a hot and difficult issue in ionospheric research. In August 2014, under the influence of a solar flare explosion and two CME events, a strong magnetic storm was triggered on 27 August, accompanied by an ionospheric storm effect. The maximum Kp index reached 4.7, and the lowest Dst index reached -80 nT, reaching the level of moderate intensity geomagnetic storm. Based on the data of global ionospheric TEC and Rate of TEC Index (ROTI), the global ionospheric effects at different sectors in August 2014 were analyzed. Possible mechanisms responsible for ionospheric disturbances were also discussed. It is found that the ionosphere in the geomagnetic storm has an obvious ionospheric storm effect. During the magnetic storm, the southern hemisphere was dominated by positive storms while the northern hemisphere was characterized by a positive storm followed by a long duration strong negative storm, and the negative phase storm duration was significantly longer than the positive storm; the amplitude variation at low latitude was smaller than that at mid-latitude and the high latitude mainly performed negative storm effects; the peaks of Equatorial Ionospheric Anomaly (EIA) disappeared after the magnetic storm occurs due to the movement of EIA towards the equator. The analysis of ionospheric irregularities during geomagnetic storms shows that ionospheric scintillation occurs before the magnetic storm at European-African sector and disappears after the geomagnetic storm. The results show that there are obvious temporal and spatial differences in the ionospheric changes during the storm.-
Key words:
- Geomagnetic storm /
- Ionosphere /
- TEC /
- ROTI
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