# Nowcasting Geoelectric Fields in Ireland using Magnetotelluric Transfer Functions

## TL;DR

This paper introduces a near real-time method for modeling geoelectric fields in Ireland using magnetotelluric transfer functions and magnetic field measurements, aiding in the mitigation of geomagnetically induced currents (GIC) affecting infrastructure.

## Contribution

The study develops and validates a novel near real-time geoelectric field modeling approach combining magnetic measurements and magnetotelluric transfer functions, optimized for rapid GIC hazard assessment.

## Key findings

- Accurately estimated electric fields with 1-minute delay during geomagnetic storms.
- Model achieved high coherence (0.70-0.85) and SNR (3.2-6.5) in validation.
- Galvanic distortion correction improved regional electric field direction consistency.

## Abstract

Geomagnetically induced currents (GIC) driven by geoelectric fields pose a hazard to ground-based infrastructure, such as power grids and pipelines. Here, a new method is presented for modelling geoelectric fields in near real time, with the aim of providing valuable information to help mitigate the impact of GIC. The method uses magnetic field measurements from the Magnetometer Network of Ireland (MagIE; \url{www.magie.ie}), interpolates the geomagnetic field variations between magnetometers using spherical elementary current systems (SECS), and estimates the local electric field using a high density ($<~40~km$) network of magnetotelluric transfer functions (MT-TF) encompassing the island. The model was optimised to work in near real time, with a correction curve applied to the geoelectric field time series. This approach was successfully validated with measured electric fields at four sites for a number of geomagnetic storms, providing accurate electric fields up to a 1-minute delay from real time, with high coherence ($0.70 - 0.85$) and signal-to-noise ratio (SNR; $3.2 - 6.5$) relative to measured electric field validation time series .This was comparable to a standard non real-time geoelectric field model (coherence$~=~0.80 - 0.89$ and SNR$~=~4.0 - 7.0$). The impact of galvanic distortion on the model was also briefly evaluated, with a galvanic distortion correction leading to a more homogeneous representation of the direction of the electric field, at a regional scale.