Mapping Geoelectric Field Hazards in Ireland.

Geoelectric fields are generated at the Earth's surface and can lead to the induction of hazardous geomagnetically induced currents (GIC) in infrastructure like power grids, railways and pipelines during geomagnetic storms. Magnitude and orientation of the geoelectric fields, in relation to the infrastructure, are key features needed to determine the intensity of GIC. Here, we developed the first geoelectric hazard map for the island of Ireland, with the aim of providing detailed information that can help stakeholders mitigate the impact of GICs. The hazard map was developed by modeling and mapping the geoelectric field across Ireland for 28 years (1991–2018) using magnetic field data with magnetotelluric transfer functions. The approach for developing the hazard map calculates the probability of exceeding a hazardous geoelectric field threshold (500 mV/km) during large geomagnetic storms, taking directionality and amplitude into account. We found hazardous geoelectric fields to be mostly localized in areas in the west, south‐west and northern coast. We observed that the geoelectric field have a stronger dominant orientation than the orientation of the geomagnetic field, often constraining the hazardous geoelectric field in particular directions only. We demonstrate a seasonal/diurnal effect is present in the geoelectric field time series. The impact of galvanic distortion was also assessed, and we demonstrate that there is a significant difference in terms of amplitude and direction between both models. Plain Language Summary: Variations in the Earth's magnetic field, during geomagnetic storms, can lead to the creation of electric fields at the surface of the Earth called geoelectric fields. Geoelectric fields can drive electrical currents known as geomagnetically induced currents (GIC) in infrastructure like power grids, railways, and pipelines. In this study, we created the first geoelectric field hazard map for Ireland. The purpose of this map is to provide a product that can help those people involved in infrastructure planning and management to reduce the impact of GIC. The results of the study indicate that areas along the northern coast, as well as the west and southwest of Ireland are more susceptible to large geoelectric fields. We found that the electric fields have a strong directional component, suggesting that the hazardous effects may occur only if the infrastructure, such as power networks are aligned in the same direction. Key Points: Geoelectric field hazard maps were generated across Ireland to evaluate the potential hazard of space weather to ground‐based infrastructureAmplitude and direction of the geoelectric field are affected by galvanic distortion, with a correction applied to examine its effectPeak geoelectric fields of 3 and 9 V/km are expected respectively for galvanic corrected and galvanic non‐corrected models [ABSTRACT FROM AUTHOR]