Simulating Geomagnetically Induced Currents using Empirical Magnetotelluric Impedances in Aotearoa New Zealand

<p><strong>This thesis is a comprehensive guide outlining physics-based simulations performed to identify vulnerabilities in Aotearoa New Zealand’s power grid network during space weather events. A growing understanding of the influences of space weather on technological systems has captured the attention of scientists spanning disciplines from astrophysics, atmospheric sciences, and geophysics. Research within these fields have indicated that the risk of large scale magnetic storms to ground based infrastructure is, to a large degree, dependent on the geology, were regions underlain by rocks having high electrical resistivity are most at risk. The electric currents induced in infrastructure and man-made technology are referred to as geomagnetically induced currents (GIC). These can result in loss of communications, pipeline corrosion, and damage to transformers, and in extreme cases blackout occurrences. The role of improving the earth conductivity models in space weather hazard studies has been underway in Aotearoa New Zealand for several years with the increasing acquisition of long period magnetotelluric (MT) data.</strong></p><p>This work incorporates GIC calculations from 62 MT impedance measurements collected in the South Island. GIC were computed using the MT data for several historical geomagnetic storms where resulting time series are compared to the direct measurements made at transformers by Transpower Ltd. Thus far, results imply that the models using the long period MT data yield GIC proximal to the measured peak storm values, more so than the previous models. The validation of this technique is a fundamental step in carrying out the assessment of GIC in the northernmost North Island, a region where no MT measurements existed, until now. Recent acquisition of 55 MT sites spanning Northland to the Waikato region are used in con- junction with legacy MT data to calculate GIC in the North Island to assess which substation transformers are most at risk to space weather hazards.</p>