Nowcasting geoelectric fields in Ireland using magnetotelluric transfer functions

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; 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.

Extreme Value Analysis of Ground Magnetometer Observations at Valentia Observatory, Ireland

“…The Magnetometer Network of Ireland (MagIE, https://www.magie.ie/), includes stations across the island of Ireland, and has been used to model the effects of GICs (Blake et al., 2016, 2018) and geoelectric fields (Campanyà et al., 2019; Malone‐Leigh et al., 2023). Most recently, Malone‐Leigh et al.…”

“…Most recently, Malone‐Leigh et al. (2023) used the MagIE network to nowcast geoelectric fields. Of course, MagIE is one of many magnetometer networks across the world, and the Valentia station in the southwest of Ireland (51.93°N, 349.75°E geographic) is a contributing station to the INTERMAGNET network (Love & Chulliat, 2013), which itself contributes to the SuperMAG data set (Gjerlov, 2012).…”

“…The Magnetometer Network of Ireland (MagIE, https://www.magie.ie/), includes stations across the island of Ireland, and has been used to model the effects of GICs (Blake et al, 2016(Blake et al, , 2018 and geoelectric fields (Campanyà et al, 2019;Malone-Leigh et al, 2023) (Love & Chulliat, 2013), which itself contributes to the SuperMAG data set (Gjerlov, 2012). In this study, data from the MagIE Valentia station is used, as it provides a broad parameter space of two solar cycles; data from 1991 to 2021 is extracted via the SuperMAG interface at 1 minute resolution.…”

“…Ground based magnetometers measure deflections in the magnetic field as a result of changes in overhead currents, which can be used to infer variations in geomagnetically induced currents (GICs, Blake et al., 2016, 2018), geoelectric fields (Campanyà et al., 2019; Malone‐Leigh et al., 2023), and the overhead currents themselves (e.g., auroral electrojet indices, Davis & Sugiura, 1966). Ground based magnetometers have been used for over a century to characterize space weather effects.…”

Multi‐Site Transfer Function Approach for Real‐Time Modeling of the Ground Electric Field Induced by Laterally‐Nonuniform Ionospheric Source

“…(2019) and Malone‐Leigh et al. (2023), where the relations between electric and magnetic fields are based on plane‐wave assumption, while the magnetic field is obtained by the interpolation from few observation sites. As for the full simulations with non‐uniform sources, there are just a few of them (e.g., Beggan, 2015; Beggan et al., 2021; Honkonen et al., 2018; Marshalko et al., 2020, 2021).…”