Geomagnetic storm impact on infrastructure - observations, modelling and prediction capability

Within the International Space Weather Action Teams (ISWAT) initiative the G1: Geomagnetic environment cluster decided to focus on three geomagnetic storm periods with varying characteristics. The focus of the G1-01 - Geoelectric Field and GIC modelling working team is on the expected and observed impacts during these storm intervals and the modelling capability of the geoelectric response. During two of the studied storms transformers triggered in the Swedish power network. The reason for the triggerings was not entirely established but has been related to the observed solar storms by the Swedish power grid operator. There were no power outages or damages to the transformers in relation to these events and the transformers were reconnected again after a couple of hours without remarks. Regional 3-D modelling taking into account a detailed 3-D structure of the conductivity in Fennoscandinavia show that both impacts occur in mid-Sweden in a region of enhanced electric fields due to the combined effect of a lower crustal conductivity in this region and 3D effects due to neighbouring high conductivity regions. Furthermore, the impacts are closely related to a large geomagnetic disturbance (GMD) over Scandinavia, with a regional maximum observed in the magnetometer station in Lycksele (LYC) only ~200 km away from the impact sites. One event was associated to a turning of the interplanetary magnetic field while the other event had no clear solar wind driving. Furthermore, the prediction capability of the Space Weather Modelling Framework (SWMF) is evaluated by investigating the capability to reproduce the observed rapid, high magnitude localized magnetic disturbances over Scandinavia that are likely to be responsible for the observed impacts in the Swedish power grid. Although SWMF does capture parts of the GMDs it cannot reproduce either the magnitude nor the regional variation. Consequently, the predicted GICs will be underestimated in the region of the observed impacts.