Monitoring and Modelling Geomagnetic and Geoelectric Fields in Ireland
Citation:
Malone-Leigh, John, Monitoring and Modelling Geomagnetic and Geoelectric Fields in Ireland, Trinity College Dublin, School of Physics, Physics, 2024Download Item:
Abstract:
Geomagnetic storms form in response to the arrival of solar storms at the Earth, which interact with the Earth's magnetic field and can lead to geomagnetic storms. Magnetic field variations generated during geomagnetic storms can interact with the subsurface geology of the Earth and in turn generate electric fields at the Earth's surface (geoelectric fields). These electric fields then drive geomagnetically induced currents in long ground-based conductors, most notably power grids, causing damage in extreme events. In this thesis, I report the research activities carried out in the last four years on the topic of modelling and monitoring geomagnetic and geoelectric fields. The main goal of this research was to monitor and expand the understanding of the potential ground-based effects across Ireland caused by space weather events. The magnetometer network of Ireland (MagIE) is a network of geomagnetic observatories first established for research by Blake (2017). Here, this network was maintained, with an additional magnetometer observatory at Dunsink added to the network. A website (www.magie.ie) was created to display real-time plots of magnetic activity and to provide access to the archived data from the network. Using magnetometer data as inputs, a spherical elementary current system (SECS) interpolation model is used to estimate the magnetic field variations across Ireland with its accuracy mapped and quantified. Measured geoelectric field time series from the space weather electromagnetic database in Ireland (SWEMDI) were used to construct a mapped three-dimensional model of geoelectric fields across the island. Transfer functions (TF) were used to relate the modelled SECS derived magnetic field to the geoelectric fields using the method from Campanya et al. (2019), with an altered version of this model optimised and validated against measurements to model geoelectric fields in near-real time (1-minute delay). Two models were considered, one with and without a galvanic distortion correction. Galvanic distortions are caused by localised near-surface inhomogeneities recorded dur- ing geoelectric field measurements, which alter the appearance of large regional struc- tures in the geoelectic field. Whether one model with or without a correction works better is not known, hence both are analysed here in parallel. Patterns in the geoelectric field were then derived by modelling geoelectric field time series between 1991 - 2019, with hazard maps used to display these regions prone to significant geoelectric fields (defined as 500 mV/km here). The geoelectric field in Ireland is found to be highly directionally polarised, with peak regions identified in the South-West and Northern coast. The main effect of a galvanic distortion correction was an alteration of the dominant direction the geoelectric field is oriented in. Finally, the effect of using three-dimensional (3D) geoelectric field inputs on mod- elled GIC was explored. A GIC model created by Blake (2017) simulated GIC in the Irish power grid using one-dimensional (1D) geoelectric field inputs. These inputs were updated to 3D geoelectric fields (both galvanic corrected and non-corrected), and compared to the 1D model to examine the effect of including directionally, compared against measured GIC. The 3D model improves on the 1D model at the validation site, with little difference between the galvanic corrected and non-corrected in terms of the performance metrics. The 3D models were simulated between 1989 - 2023, with the largest GIC expected in the South-West and Eastern coast. In particular, the Moneypoint site in the South-West of the island was prone to large GIC, with a maximum of 105/120 A (corrected/non-corrected) modelled for the November, 1991 geomagnetic storm, with the largest duration in excess of 10 A (defined as the beginning of hazardous conditions) for 153/181 (corrected/non-corrected) minutes during the Halloween, 2003 geomagnetic storm.
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Grant Number
Irish Research Council (IRC)
EPSPG/2020/96
Author's Homepage:
https://tcdlocalportal.tcd.ie/pls/EnterApex/f?p=800:71:0::::P71_USERNAME:JMALONELDescription:
APPROVED
Author: Malone-Leigh, John
Sponsor:
Irish Research Council (IRC)Advisor:
Gallagher, PeterCampanya, Joan
Publisher:
Trinity College Dublin. School of Physics. Discipline of PhysicsType of material:
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