Geomagnetically Induced Currents Caused by Interplanetary Shocks With Different Impact Angles and Speeds
Geomagnetically Induced Currents Caused by Interplanetary Shocks With Different Impact Angles and Speeds
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DOI：
10.1029/2018sw001880
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发表时间：
2018-06
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通讯作者：
D. M. Oliveira;D. M. Oliveira;D. Arel;Joachim Raeder;E. Zesta;C. Ngwira;C. Ngwira;Brett Carter;E. Yizengaw;Alexa J. Halford;B. Tsurutani;Jesper Gjerloev;Jesper Gjerloev
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作者：
D. M. Oliveira;D. M. Oliveira;D. Arel;Joachim Raeder;E. Zesta;C. Ngwira;C. Ngwira;Brett Carter;E. Yizengaw;Alexa J. Halford;B. Tsurutani;Jesper Gjerloev;Jesper Gjerloev
地磁感应电流(GIC)的出现对现代技术基础设施构成严重威胁。大的GIC是由于大尺度磁层和电离层电流的变化引起的地磁场(分贝/dt)的急剧变化造成的。众所周知，由于风暴时间的亚暴，高纬度地区经常发生强烈的分贝/分贝/分贝微扰。通常由行星际激波引起的磁层压缩增加了磁层顶电流，导致中纬度到低纬度地区的分贝/dt扰动更加明显，同时它们增加了赤道电喷流，导致日侧赤道区域的分贝/dt扰动。我们利用在L1点观测到的547个激波的数据库，研究了冲击角度和速度对随后的分贝/dt扰动的影响。通过采用作为电力系统风险因素的分贝/分贝/分=100 nT/min的阈值，我们发现，在日侧高纬度地区发生高速和接近锋面的冲击时，分贝/分贝通常会超过这个分贝/分贝。同样的趋势出现在较低纬度和所有夜间事件，但高危事件较少。特别是，我们在赤道位置发现了9个分贝/dt>；100nT/min的事件。所有事件都是由高速和接近正面的冲击波撞击引起的，并由当地时间中午左右的站点观测到。这些高风险的扰动是由突然的强烈和对称的磁层压缩引起的，更有效地加强了赤道电喷流，导致了急剧的分贝/dt扰动。我们认为，这些结果可能为旨在防止电力系统因GIC而退化的GIC预测提供启示。
The occurrence of geomagnetically induced currents (GICs) poses serious threats to modern technological infrastructure. Large GICs result from sharp variations of the geomagnetic field (dB/dt) caused by changes of large‐scale magnetospheric and ionospheric currents. Intense dB/dt perturbations are known to occur often in high‐latitude regions as a result of storm time substorms. Magnetospheric compressions usually caused by interplanetary shocks increase the magnetopause current leading to dB/dt perturbations more evident in midlatitude to low‐latitude regions, while they increase the equatorial electrojet current leading to dB/dt perturbations in dayside equatorial regions. We investigate the effects of shock impact angles and speeds on the subsequent dB/dt perturbations with a database of 547 shocks observed at the L1 point. By adopting the threshold of dB/dt = 100 nT/min, identified as a risk factor to power systems, we find that dB/dt generally surpasses this threshold when following impacts of high‐speed and nearly frontal shocks in dayside high‐latitude locations. The same trend occurs at lower latitudes and for all nightside events but with fewer high‐risk events. Particularly, we found nine events in equatorial locations with dB/dt > 100 nT/min. All events were caused by high‐speed and nearly frontal shock impacts and were observed by stations located around noon local time. These high‐risk perturbations were caused by sudden strong and symmetric magnetospheric compressions, more effectively intensifying the equatorial electrojet current, leading to sharp dB/dt perturbations. We suggest that these results may provide insights for GIC forecasting aiming at preventing degradation of power systems due to GICs.