The surface electric field induced by external geomagnetic source fields is modeled for a continental-scale 3-D electrical conductivity model of Australia at periods of a few minutes to a few hours. The amplitude and orientation of the induced electric field at periods of 360 s and 1800 s are presented and compared to those derived from a simplified ocean-continent (OC) electrical conductivity model. It is found that the induced electric field in the Australian region is distorted by the heterogeneous continental electrical conductivity structures and surrounding oceans. On the northern coastlines, the induced electric field is decreased relative to the simple OC model due to a reduced conductivity contrast between the seas and the enhanced conductivity structures inland. In central Australia, the induced electric field is less distorted with respect to the OC model as the location is remote from the oceans, but inland crustal high-conductivity anomalies are the major source of distortion of the induced electric field. In the west of the continent, the lower conductivity of the Western Australia Craton increases the conductivity contrast between the deeper oceans and land and significantly enhances the induced electric field. Generally, the induced electric field in southern Australia, south of latitude −20°, is higher compared to northern Australia. This paper provides a regional indicator of geomagnetic induction hazards across Australia. <b>Citation:</b> Wang, L., A. M. Lewis, Y. Ogawa, W. V. Jones, and M. T. Costelloe (2016), Modeling geomagnetic induction hazards using a 3-D electrical conductivity model of Australia, <i>Space Weather</i>, 14, 1125–1135, doi:10.1002/2016SW001436

Abstract: Geomagnetic storms can cause power grid instabilities and blackouts due to excessive geomagnetically induced currents (GICs) flowing in electric transmission systems. In this study, we assess regional vulnerability to GICs by modeling the geoelectric fields induced by significant historic geomagnetic disturbance events in the presence of 3D subsurface geology using data from the Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) magnetotelluric array, Australia‐Wide Array of Geomagnetic Stations (AWAGS) magnetometer array, and Geoscience Australia geomagnetic observatory network. We analyze the vertical component of the magnetic field with respect to the horizontal magnetic‐field polarization for two magnetic storms and gain insight into the inductive effects associated with field polarization orientations in the 3D case. We also analyze the telluric field intensity and polarization for a unit geomagnetic field polarized in northerly and easterly directions at AusLAMP sites and find that in the presence of 3D geology the induced field has a very polarization‐sensitive anomaly. We model the geoelectric fields in southeastern Australia for the 1989 “Québec storm.” The induced ground electric fields are typically in the range 1,000–2,000 mV/km with a few sites within 2,000–5,000 mV/km on highly resistive regions and in coastal areas, and below 300 mV/km on inland sedimentary basins. The current study focuses on magnetic field variations with periods between 120 and ~20,000 s due to bandwidth limits in our magnetotelluric tensor data and the Nyquist limit for the 60 s sampling of our geomagnetic‐field data. Hence, our modeled maximum values should be considered lower estimates of potential real values. Plain Language Summary: We assess Australia's vulnerability to electric currents caused by geomagnetic storms. We use data from recent and historic geophysical studies to represent a range of possible geomagnetic‐field variations (including the extreme 1989 “Québec storm” event), and we use a three‐dimensional mathematical representation of the electrical conductivity of Australia's regional geology to represent the natural conductors in which electric currents can flow. Our analysis shows that the spatial variability of ground electric currents that can be caused by geomagnetic storms is closely associated with geologic structure. We find that ground electric currents are stronger in places where there are large differences between the conductivities of subsurface geologic structures. These include, for example, electrically resistive rocks near coastlines that are adjacent to deep and highly conductive oceans or, inland, where there are big contrasts between the electrical conductivities of different rock types. Away from such natural differences in electrical conductivity ground electric currents tend to be weaker. Every country on Earth has different types of rock that make up its geology, and many countries are bounded by an ocean. Vulnerability to electric currents caused by geomagnetic storms is an increasingly important issue, particularly in light of the mushrooming reliance of societies on high‐tech solutions to modern needs. The method we have developed for this research is readily extensible to other places to assess the risk posed by ground electric currents. <b>Citation:</b> Wang, L., Duan, J., Hitchman, A. P., Lewis, A. M., & Jones, W. V. (2020). Modeling geoelectric fields induced by geomagnetic disturbances in 3D subsurface geology, an example from Southeastern Australia. <i>Journal of Geophysical Research: Solid Earth</i>, 125, e2020JB019843. https://doi.org/10.1029/2020JB019843

Geoscience Australia’s geomagnetic observatory network covers one-eighth of the Earth. The first Australian geomagnetic observatory was established in Hobart in 1840. This almost continuous 180-year period of magnetic-field monitoring provides an invaluable dataset for scientific research. Geomagnetic storms induce electric currents in the Earth that feed into power lines through substation neutral earthing, causing instabilities and sometimes blackouts in electricity transmission systems. Power outages to business, financial and industrial centres cause major disruption and potentially billions of dollars of economic losses. The intensity of geomagnetically induced currents is closely associated with geological structure. We modelled peak geoelectric field values induced by the 1989 Québec storm for south-eastern Australian states using a scenario analysis. Modelling shows the 3D subsurface geology had a significant impact on the magnitude of induced geoelectric fields, with more than three orders of magnitude difference across conductive basins to resistive cratonic regions in south-eastern Australia. We also estimated geoelectrically induced voltages in the Australian high-voltage power transmission lines by using the scenario analysis results. The geoelectrically induced voltages may exhibit local maxima in the transmission lines at differing times during the course of a magnetic storm depending on the line’s spatial orientation and length with respect to the time-varying inducing field. Real-time forecasting of geomagnetic hazards using Geoscience Australia’s geomagnetic observatory network and magnetotelluric data from the Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) helps develop national strategies and risk assessment procedures to mitigate space weather hazard. This Abstract was submitted/presented to the 2023 Australian Exploration Geoscience Conference 13-18 Mar (https://2023.aegc.com.au/)

Space weather manifests in power networks as quasi‐DC currents flowing in and out of the power system through the grounded neutrals of high‐voltage transformers, referred to as geomagnetically induced currents. This paper presents a comparison of modeled geomagnetically induced currents, determined using geoelectric fields derived from four different impedance models employing different conductivity structures, with geomagnetically induced current measurements from within the power system of the eastern states of Australia. The four different impedance models are a uniform conductivity model (UC), one‐dimensional n‐layered conductivity models (NU and NW), and a three‐dimensional conductivity model of the Australian region (3DM) from which magnetotelluric impedance tensors are calculated. The modeled 3DM tensors show good agreement with measured magnetotelluric tensors obtained from recently released data from the Australian Lithospheric Architecture Magnetotelluric Project. The four different impedance models are applied to a network model for four geomagnetic storms of solar cycle 24 and compared with observations from up to eight different locations within the network. The models are assessed using several statistical performance parameters. For correlation values greater than 0.8 and amplitude scale factors less than 2, the 3DM model performs better than the simpler conductivity models. When considering the model performance parameter, P, the highest individual P value was for the 3DM model. The implications of the results are discussed in terms of the underlying geological structures and the power network electrical parameters. <b>Citation:</b> Marshall, R. A., Wang, L., Paskos, G. A., Olivares‐Pulido, G., Van Der Walt, T., Ong, C., et al. (2019). Modeling geomagnetically induced currents in Australian power networks using different conductivity models. <i>Space Weather</i>, 17. https://doi.org/10.1029/2018SW002047

<div>Dr Francois Chamalaun passed away in Adelaide, Australia, in April 2024. Francois was a Senior Lecturer in Geophysics at Flinders University in South Australia and foundation Chairman of its School of Earth Sciences. He was an internationally respected scientist, enthusiastic teacher, and valued mentor. His 40-year research career led to new insights into the electrical structure of the Earth and its atmosphere, particularly in Australia, Brazil, Indonesia, India, and New Zealand.</div><div><br></div><div>Much of this research was made possible through the development by Francois and Flinders University technical officer Bob Walker of a portable self-contained microprocessor-based three-component magnetometer. This is a short reflection on the use of this innovative instrument in the first-of-its-kind Australia-Wide Array of Geomagnetic Stations (AWAGS). <b>Citation:</b> Wang, L., Greenhalgh, S., Barton, C., Heinson, G., & Hitchman, A. (2024). Vale: Francois Chamalaun (1937 – 2024). <i>Preview</i>, 2024(232), 15–18. https://doi.org/10.1080/14432471.2024.2412324

A geomagnetic storm, also known as a geomagnetic disturbance (GMD), is a major disturbance of the Earth’s magnetic field caused by solar activity. A geomagnetic storm induces electric currents in the Earth that feed into power lines through substation neutral earthing, causing instabilities and even blackouts in electricity transmission systems. The intensity of geomagnetically induced currents (GICs) is closely associated with the electrical conductivity of the surrounding geology. In this paper, we analyse one of the most well-known geomagnetic storms, the 1989 “Québec storm” and 688 magnetotelluric (MT) survey sites from the Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) to gain insight into the space weather hazard posed for Australia's modern-day power grids. Transmission lines may exhibit local maxima at differing times depending on their spatial orientation and length with respect to the time-varying magnetic field. Localised peak voltages over 100 V can be observed on some individual lines. This assessment identifies the distribution of GICs in south-eastern Australia for the 1989 Québec storm and transmission lines that are more vulnerable to GICs. It is relevant to national strategies and risk assessment procedures to mitigate space weather hazards in the Australian high-voltage power grid and the design of a more resilient power transmission system. We also analyse the 2015 “St Patrick’s Day storm” to study under-estimation of the space weather hazard associated with the band-limited geomagnetic data and MT data sets. <b>Citation:</B> Liejun Wang, Jingming Duan, Adrian P. Hitchman, Matthew G. Gard, Richard A. Marshall, Andrew M. Lewis & William V. Jones (2023) AusLAMP shines a light on space weather hazards in the Australian high-voltage power grid, <i>Exploration Geophysics</i>, DOI: 10.1080/08123985.2023.2281617

A geomagnetic storm, also known as a geomagnetic disturbance (GMD), is a major disturbance of the Earth’s magnetic field caused by solar activity. A geomagnetic storm induces electric currents in the Earth that feed into power lines through substation neutral earthing, causing instabilities and even blackouts in electricity transmission systems. The strength of geomagnetically induced currents (GICs) in the ground is directly related to the electrical conductivity of the surrounding geology. GICs experienced within power transmission lines are also influenced by the orientations and configuration of the power lines with respect to the electric fields. We installed a geoelectric field monitoring system at the Canberra geomagnetic observatory (CNB) to directly measure geomagnetically induced electric fields. This data enhances the capability in modelling and forecasting geoelectric hazards and can be used to validate the modelling approach through convolving magnetotelluric (MT) tensors with geomagnetic fields. In this presentation, we modelled the induced electric fields for the 1989 Québec geomagnetic storm, using MT data collected at survey sites from the Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP). These results give us insight into the potential magnitude of space weather hazards to Australia's modern-day power grids. We extended this approach to a ‘Carrington-class’ geomagnetic storm to evaluate geoelectric fields in the Australian region, allowing GICs flow in the power lines to be estimated. As an example, geomagnetically induced voltages in transmission lines from Queensland for a ‘Carrington-class’ geomagnetic storm are presented. Presented at the 2024 Australian Society of Exploration Geophysicists (ASEG) 2024 Discover Symposium

<div>This report contains information about the operation of Geoscience Australia’s ten permanent geomagnetic observatories, repeat stations and other relevant information covering the period from 2017 to 2021.</div><div>Information regarding the activities and services of Geoscience Australia’s Geomagnetism program, distribution of geomagnetic data, geomagnetic instrumentation and data processing procedures is also provided.</div><div><br></div>

The Australia-Wide Array of Geomagnetic Stations survey was an array of 58 vector magnetometers covering mainland Australia, but not Tasmania, and comprised 54 portable three-component magnetometers plus four permanent magnetic observatories. Time-series of geomagnetic field fluctuations were recorded at 1-minute intervals with 1 nanoTesla sensitivity, together with sensor temperature and time. The portable magnetometers in the array were programmed to commence recording simultaneously on 18 November 1989. Most instruments were kept operating for a nominal interval of 8 months. The last data were recorded on 17 December 1990. The survey was run jointly by Flinders University of South Australia and Geoscience Australia (previously the Australian Geological Survey Organisation). Further details are available: Welsh, W. D. and Barton, C. E. (1996), The Australia-Wide Array of Geomagnetic Stations (AWAGS): data corrections. AGSO Record 1996/54, Australian Geological Survey Organisation, Canberra.

There are a number of global initiatives to understand and mitigate the impacts of extreme space weather on critical infrastructure and modern society. This paper provides the results of an analysis to estimate extreme geoelectric field values for the Australian region to facilitate evaluation of Australia's power system response to extreme geomagnetic storms. Geoelectric fields are calculated using a grid of modeled magnetotelluric impedance tensors obtained from a 3‐D conductivity model of the Australian region. Statistical metrics derived from grids of geoelectric field time series are analyzed as a function of Dst index for different storm days to extrapolate geoelectric fields to extreme storm levels over a range of ground conductivity conditions. For Carrington event storm levels, geoelectric field values of 5.3 ± 3.8 V/km in the north‐south direction and 9.6 ± 4.3 V/km in the east-west direction are expected for areas of electrically resistive rocks near coastlines that are adjacent to deep highly conductive oceans, and inland, where there are large contrasts between the electrical conductivities of different rock types across Australia. Further, geoelectric field values may change by at least an order of magnitude over the grid spacing interval of 50 km in these areas. The results of the analysis also suggest that upscaling grids of geoelectric field time series derived from an observed storm by the ratio of extreme storm Dst to the observed storm Dst are a valid approach for the Australian region that provides extreme storm scenarios for different storm morphologies. <b>Citation:</b> Marshall, R., Dziura, L., Wang, L., Young, J., & Terkildsen, M. (2020). Estimating extreme geoelectric field values for the Australian region. <i>Space Weather</i>, 18, e2020SW002512. https://doi.org/10.1029/2020SW002512