Proximity Effects of Lateral Conductivity Variations on Geomagnetically Induced Electric Fields

During a magnetic storm, the induced geoelectric field drives geomagnetically induced currents (GIC) in power transmission networks, railway systems, and pipelines, negatively affecting these systems. In regions with complex geological structures, the lateral earth conductivity changes influence the induced electric field distribution in the earth. H- and E-polarization are two cases of the orientation of the E-field vector relative to the lateral changes. A model of the earth with lateral conductivity changes is established in this paper to examine the effects of conductivity change across a discontinuity on the magnitude of the E-field for the case of the E-field parallel to the discontinuity. The electric field distribution with distance from the discontinuity is calculated, and the relationship between the lateral conductivity changes and electric field distortion is analyzed using the finite element method. In addition, the GIC variation in the power grid due to the lateral conductivity changes is examined. Then, the factors affecting GIC, including conductivity, frequency, and distance, are investigated. The results show that lateral conductivity changes can infiuence the GIC in power lines running parallel to the discontinuity up to 250 km from the discontinuity. The methods and results are significant for understanding how lateral conductivity changes influence GIC and will improve the accuracy of GIC calculations.