[S-EM14] Electric, magnetic and electromagnetic survey technologies and scientific achievements

[SEM14-16] Simulation and Analysis of Geomagnetically Induced Current (GIC) in Japan including a three-dimensional ground inhomogeneity

★Invited Papers

*中村 紗都子¹、海老原 祐輔²、亘 慎一³、藤田 茂⁴、後藤 忠徳⁵ (1.名古屋大学宇宙地球環境研究所、2.京都大学生存圏研究所 、3.情報通信研究機構 、4.情報システム研究機構、データサイエンス共同利用基盤施設/統計数理研究所 、5.兵庫県立大学大学院理学研究科 )

We modeled the time series of geomagnetically induced currents (GICs) flowing in the Japanese 500 kV power grid. The three-dimensional distribution of the electric field was calculated using the finite-difference time-domain (FDTD) method. A three-dimensional electrical conductivity model was constructed from a global relief model and a global map of sediment thickness. First, we imposed a uniform sheet current at 100 km altitude to illuminate the influence of the structured ground conductivity. The simulation result shows that geomagnetically induced electric field (GIE) exhibits localized, uneven distribution that can be attributed to charge accumulation due to the inhomogeneity below the Earth's surface. The charge accumulation becomes large when the conductivity gradient is parallel to the incident electric field. Using the uneven distribution of GIE, we calculated the GICs flowing in a simplified 500 kV power grid network in Japan. The influence of the structured ground conductance on GIC appears to depend on a combination of the location of substations and the direction of the source current. Uneven distribution of the power grid system gives rise to intensification of the GICs flowing inremote areas where substations/power plants are distributed sparsely. Secondly, we used the equivalent current inferred from the ground magnetic disturbance for some magnetic storms. We show the sensitivity of the GIC magnitude on the three-dimensional ground inhomogeneity.