Assessing the risk posed by Geomagnetically Induced Currents (GICs) to the regular operation of power grids requires a hazard specification in terms of the induced geoelectric field (GEF). In order to specify the GIC hazard posed to the German high-voltage transmission grid, we model the GEF within Germany for geomagnetically disturbed conditions using magnetic field measurements from INTERMAGNET observatories and a predefined electrical conductivity model of the subsurface as input. This contribution focuses on a comparison of GEFs modeled assuming electromagnetic (EM) induction scenarios of different complexity, which are imposed through the specification of the inducing EM field on the one hand and the dimensionality of the conductivity model on the other. The former is specified either as a plane wave or a laterally varying field obtained by fitting Spherical Elementary Current Systems basis functions to the magnetic field observations. The conductivity distribution is given either by the “EURHOM” model or our new dedicated 3D model for Germany obtained from legacy magnetotelluric data. The latter also includes realistic 3D conductivity variations due to the ocean/sea and marine sediments, which are known to affect magnetotelluric impedance tensors at GIC-relevant frequencies near coastlines. Based on the modeled GEFs, we calculate GICs exemplarily at selected substations and geomagnetic disturbance events. The results indicate the level of complexity needed in the GEF modeling in order to derive meaningful GIC hazard maps for Germany down the line.

The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)