Geomagnetically induced currents (GIC)

Antti Pulkkinen
Finnish Meteorological Institute

Geomagnetically induced currents (GIC) in technological systems, such as electric power transmission grids, oil and gas pipelines, telecommunication cables and railway equipment, are harmful space weather effects at the Earth's surface. In power systems GIC cause saturation of transformers, which may lead to serious problems and even to a collapse of the whole system or to permanent damage of transformers. In buried pipelines GIC give rise to corrosion problems. GIC are driven by the geoelectric field induced by geomagnetic variations. The electric and magnetic fields primarily depend on ionospheric currents and secondarily on currents induced in the Earth.

GIC and the associated geoelectromagnetic processes have been studied for more than two decades at the Finnish Meteorological Institute. During this period several methods for the calculation of the surface electromagnetic fields and actual GIC in technological systems have been developed and applied to Finnish networks. Studies made for the Finnish power and pipeline industry have been a solid part of the GIC research made at FMI. Present studies are concentrating on understanding characteristics of the ionospheric currents during intense geomagnetic disturbances leading to large GIC.