Regional 3-D Modeling and Verification of Geomagnetically Induced Currents in Sweden

Geomagnetically induced currents (GICs) flowing in long conductors can pose a threat to critical infrastructure such as the power grid in cases of extreme geomagnetic activity. Geomagnetic activity is more pronounced at high latitudes; thus, Nordic countries, such as Sweden, can potentially be vulnerable to GIC. Previous studies have identified the southern region of Sweden as the most vulnerable to extreme space weather, but these studies have relied on 1-D models of the ground conductivity. Sweden, however, has large lateral variations in the underlying ground conductivity structure across the country. Thus, the understanding of the ground response to space weather events cannot be captured by 1-D models. In this paper, we utilize a 3-D crustal conductivity map with surrounding oceans to model the geoelectric ground response due to a uniform magnetic field. We show that southern Sweden is exposed to stronger electric fields due to a combined effect of a low crustal conductivity and the influence of the coast-land interface from both the east and the west coast. The model can further be used to calculate GICs in the Swedish power grid and has been validated by GIC measurements from a site in northern Sweden. The measured and predicted GIC amplitudes are in excellent agreement. The model can be used to quantitatively asses the hazard from space weather in Sweden. Upon further validation at additional sites it can be used as a powerful predictive tool of the response to extreme space weather events in the Swedish power network.