Present day challenges in understanding the geomagnetic hazard to national power grids

Solar activity gives rise to changes in the near- Earth space environment, often referred to as space weather, that can adversely affect technologies on and above the surface of the Earth. For example, the impact of a coronal mass ejection on the Earth’s protective magnetosphere can lead to a geomagnetic storm, boosting existing magnetospheric currents. These current systems cause large magnetic variations that induce electric fields in the solid Earth. These fields, in turn, generate geomagnetically induced currents (GICs) that flow in conducting pipes and wires, in ways influenced by the electrical properties of each network. Consequently, power grids and pipeline networks at all latitudes are at risk from the natural hazard of GICs. As solar activity begins to increase from the deepest solar minimum in a century, we consider the current understanding of this hazard, as it affects major power systems in Europe and Africa. We also summarise what can be said with some certainty about the hazard and what research is yet required to address outstanding questions and develop useful tools for geomagnetic hazard mitigation.