Geolectric field measurement, modelling and validation during geomagnetic storms in the UK
Geolectric field measurement, modelling and validation during geomagnetic storms in the UK
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DOI：
10.1051/swsc/2021022
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发表时间：
2021-06-18
影响因子：
3.3
通讯作者：
Thomson, Alan W. P.
中科院分区：
文献类型：
--
作者：
Beggan, Ciaran D.;Richardson, Gemma S.;Thomson, Alan W. P.
显著的地电场是由快速变化的磁场与导电地球的相互作用产生的，特别是在强烈的地磁活动期间。虽然通常无害，但大的或持续的地电场可能会通过地磁感应电流（GIC）损坏接地基础设施，如高压变压器和管道。了解空间气象对地面基础设施的影响的一个关键方面是通过地电场的空间和时间变化。在全球范围内，很少有地电场的长期监测站点，因此在2012年开始在英国的勒威克，Eskdalemuir和哈特兰观测站测量水平表面场。在2012年至2020年期间，在2015年3月的风暴期间，观测到的地电场最大值在勒威克约为1 V/km，在Eskdalemuir为0.5 V/km，在哈特兰为0.1 V/km。这些长期观测还允许与地电场模型进行比较。我们使用的测量计算在每个观测站的大地电磁阻抗传递函数的周期从20到30,000秒。然后，这些被用来预测在选定的风暴期间，与记录的场非常匹配（相关性约为0.9）的观测点的地电场。我们还计算地电场值从英国的薄片模型，占不同的地质和水深岛屿设置。我们发现，薄片模型捕捉的峰值和相位的带通地电场相当不错，线性相关性一般在0.4左右。从这两个建模方法，我们产生的地电场值的历史风暴（1989年3月和2003年10月），并找到过去的峰值地电场的估计高达1.75 V/km的Eskdalemuir。然而，来自这些风暴期间高压Transformer GIC测量的证据表明，这些估计值可能低估了真实值。
Significant geoelectric fields are produced by the interaction of rapidly varying magnetic fields with the conductive Earth, particularly during intense geomagnetic activity. Though usually harmless, large or sustained geoelectric fields can damage grounded infrastructure such as high-voltage transformers and pipelines via geomagnetically induced currents (GICs). A key aspect of understanding the effects of space weather on grounded infrastructure is through the spatial and temporal variation of the geoelectric field. Globally, there are few long-term monitoring sites of the geoelectric field, so in 2012 measurements of the horizontal surface field were started at Lerwick, Eskdalemuir and Hartland observatories in the UK. Between 2012 and 2020, the maximum value of the geoelectric field observed was around 1 V/km in Lerwick, 0.5 V/km in Eskdalemuir and 0.1 V/km in Hartland during the March 2015 storm. These long-term observations also allow comparisons with models of the geoelectric field to be made. We use the measurements to compute magnetotelluric impedance transfer functions at each observatory for periods from 20 to 30,000 s. These are then used to predict the geoelectric field at the observatory sites during selected storm times that match the recorded fields very well (correlation around 0.9). We also compute geoelectric field values from a thin-sheet model of Britain, accounting for the diverse geological and bathymetric island setting. We find the thin-sheet model captures the peak and phase of the band-passed geoelectric field reasonably well, with linear correlation of around 0.4 in general. From these two modelling approaches, we generate geoelectric field values for historic storms (March 1989 and October 2003) and find the estimates of past peak geoelectric fields of up to 1.75 V/km in Eskdalemuir. However, evidence from high voltage transformer GIC measurements during these storms suggests these estimates are likely to represent an underestimate of the true value.