Estimating the electric field response to the Halloween 2003 and September 2017 magnetic storms across Scotland using observed geomagnetic fields, magnetotelluric impedances and perturbation tensors
Estimating the electric field response to the Halloween 2003 and September 2017 magnetic storms across Scotland using observed geomagnetic fields, magnetotelluric impedances and perturbation tensors
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DOI：
10.1051/swsc/2020049
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发表时间：
2020
影响因子：
3.3
通讯作者：
F. Simpson;K. Bahr
中科院分区：
文献类型：
--
作者：
F. Simpson;K. Bahr
地磁暴产生的磁变活动加剧，从而产生电场，驱动称为地磁感应电流（GIC）的危险电流通过人造技术导体，包括输电线路，铁路网络和天然气管道。我们将来自苏格兰和英格兰北方23个地点的大地电磁（MT）阻抗与2003年万圣节和2017年9月风暴的地磁场谱相乘，以估计这些风暴的最大峰间、电场幅度和方向，我们将其作为危险图呈现。通过采样这些电场在最长的方向（>50公里），高压（275和400千伏）苏格兰输电线路和集成沿着他们的长度，我们估计其相关的传输线电压。地球中的横向电导率变化产生水平磁场梯度。我们调查这些梯度对电场估计使用远程磁场的影响，通过施加校正来自本地MT站点和远程磁场站点之间的磁扰动张量的阻抗张量。对于2017年9月的风暴，我们还将我们估计的电场与一个独特的数据集进行了比较，该数据集包括来自7个MT站点的测量风暴时间电场。我们发现，峰峰值，电场幅度可能已达到13 V/km在万圣节风暴在苏格兰高地的一些地区，与线平均电场>5 V/km持续沿着一些长距离，高压输电线路; 2017年9月风暴的线平均电场为1 V/km或更小。我们的表面电场显示出显著的站点到由于地球内部的三维导电性结构而产生的场地变化，其特征在于MT阻抗张量。
Geomagnetic storms generate heightened magnetovariational activity, which induces electric fields that drive hazardous currents known as geomagnetically induced currents (GICs) through man-made technological conductors including power transmission lines, railway networks and gas pipelines. We multiply magnetotelluric (MT) impedances from 23 sites in Scotland and northern England with measured geomagnetic field spectra from the Halloween 2003 and September 2017 storms to estimate maximum peak-to-peak, electric field magnitudes and directions for these storms, which we present as hazard maps. By sampling these electric fields in the direction of the longest (>50 km), high-voltage (275 and 400 kV) Scottish power transmission lines and integrating along their lengths, we estimate their associated transmission-line voltages. Lateral electrical conductivity variations in the Earth generate horizontal magnetic field gradients. We investigate the effect of these gradients on electric field estimates obtained using remote magnetic fields by applying a correction to the impedance tensor derived from the magnetic perturbation tensor between the local MT site and the remote magnetic field site. For the September 2017 storm, we also compare our estimated electric fields with a unique dataset comprising measured storm-time electric fields from 7 MT sites. We find that peak-to-peak, electric field magnitudes may have reached 13 V/km during the Halloween storm in some areas of the Scottish Highlands, with line-averaged electric fields >5 V/km sustained along a number of long-distance, high-voltage power transmission lines; line-averaged electric fields for the September 2017 storm are 1 V/km or less. Our surface electric fields show significant site-to-site variability that arises due to Earth’s internal 3D electrical conductivity structure, as characterised by the MT impedance tensors.