华北地区地电暴时GIC及涡旋电流响应分析

通过地电场台址近地表介质电阻率和地电场值计算大地电流,从大地电流场中分离出涡旋电流;根据平面波理论和水平导电层模型,使用地磁暴观测数据在频率域计算地磁感应电场(GIE),由GIE计算地磁暴感应电流(GIC).计算结果与实测值对比分析表明:GIE计算结果与实测地电暴具有很好的相位一致性;GIC涡旋中心相对地电暴涡旋中心存在向SE漂移约3°的现象;磁暴时地磁场Z分量的幅值分布图中极大值区域与涡旋中心重合,可能是GIC涡旋中心偏移的原因.另外,根据电磁感应原理提出的等效环电流模型,在一定程度上解释了涡旋大地电流的形成机制.本项工作可应用于地磁观测与地电观测的相互校正,同时有助于认识地电暴对大地电流分布的影响.

Analysis of GIC and vortex current responses in Huabei region during geoelectric storms

Firstly, we got the telluric current by calculating geoelectric field and near-surface media resistivity around the geoelectric station sites, and then separated the vortex current from the telluric current field; Secondly, we calculated the geomagnetic induction electric field (GIE) in frequency domain using the observed geoelectric storm data, according to plane wave theory and horizontal electric layer model; Finally, we got the geomagnetically induced currents (GIC) calculated by GIE. Comparing the calculated results with the measured values, it showed that: the results of GIE and the measured geoelectric storms had good phase congruency; the GIC vortex center was drifted about 3° SE relative to the geoelectric storm vortex's; when the magnetic storm happened, the maximum region in the amplitude contour map of the Z component of the geomagnetic field was coincident with the vortex center, it may be responsible for the GIC vortex center drift. The equivalent ring current model based on electromagnetic induction principle may help explain the mechanism of how the vortex current form in a certain degree. This work can be applied to the inter-calibration of geomagnetic and geoelectric observation, meanwhile, it's useful for recognizing the geoelectric storm influence on the distribution of telluric current.