SWR5 – Advancements in Geomagnetically Induced Currents (GICs): Simulation, Monitoring, and Mitigation Strategies

Talks

SWR5.1 Tue 5/11 09:00-10:15, room C2B – Sofia

Author(s): Craig J. Rodger, Daniel H. Mac Manus, John Malone-Leigh, Mark A. Clilverd, Mikhail Kruglyakov, Kristin Pratscher, Malcolm Ingham, Wiebke Heise, Andrew Renton, Michael Dalzell, Tanja Peterson, James Brundell

Department of Physics, University of Otago, Dunedin, New Zealand; Department of Physics, University of Otago, Dunedin, New Zealand; Department of Physics, University of Otago, Dunedin, New Zealand; British Antarctic Survey (UKRI- NERC), Cambridge, United Kingdom; Department of Physics, University of Otago, Dunedin, New Zealand; Victoria University of Wellington, Wellington, New Zealand; Victoria University of Wellington, Wellington, New Zealand; GNS Science, Lower Hutt, New Zealand; Transpower New Zealand Limited, Wellington, New Zealand; Transpower New Zealand Limited, Wellington, New Zealand; GNS Science, Lower Hutt, New Zealand; Transpower New Zealand Limited, Wellington, New Zealand

Abstract: In early May 2024 the giant sunspot complex AR3664 launched ~6 Coronal Mass Ejections towards the Earth, which triggered the G5 “Gannon” geomagnetic storm. This disturbance lasted from ~17 UT on 10 May 2024 to ~9UT on 12 May 2024, producing auroral displays to comparatively low latitudes, and appears to be the largest geomagnetic disturbance in the last ~30 years. In 2022 space physics researchers worked with the New Zealand power grid system operator, Transpower New Zealand Ltd, to develop an “All of New Zealand” GIC mitigation strategy in the form of targeted line disconnections. The goal was to reduce GIC magnitudes and durations at transformers at most risk to GIC during large geomagnetic storms, while still maintaining the continuous supply of power throughout New Zealand. This strategy was declared operational in 2023, following training of control room staff. It was the result of many years of industry-research collaboration.

Once the May 2024 storm disturbance levels reached the G5 threshold, the GIC mitigation strategy was enacted by the Transpower control room staff following the plan protocols. The mitigation remained in place until 16UT on 12 May 2024, after which the circuits were restored. There was no impact to New Zealand’s electrical supply from this storm. In this presentation we will discuss the measurements made in and around the New Zealand power grid during this event. This includes GIC measured at >70 transformers. The peak GIC observed was ~113 A at a transformer in Dunedin, after the mitigation strategy was in place. High time resolution harmonic distortion observed using a VLF radio receiver by the transformer. GIC modelling will be contrasted with GIC observations to highlight what would have been expected without the mitigation measures.

This research is part of the New Zealand Solar Tsunamis programme.

Author(s): Jordan A. Guerra, Chris Balch, Anna Kelbert, E. J. Rigler, Greg Lucas

CIRES CU/SWPC NOAA; CIRES CU/SWPC NOAA; USGS; USGS; LASP CU

Abstract: The NOAA-USGS Geoelectric model is a collaboration between the National Ocean and Atmospheric Administration’s (NOAA) Space Weather Prediction Center and the U.S. Geological Survey’s (USGS) Geomagnetism Program. The product provides estimates of geoelectric fields across the continental United States (CONUS) at a one-minute cadence. This product aids stakeholders, such as power companies, in determining the potential impacts of space weather events on their systems and taking mitigation actions. The product has two main components: 1) the magnetic interpolator, which uses ground magnetic field measurements from USGS and the National Resources Canada observatories and creates a map of geomagnetic fields using the Spherical Elementary Current System (SECS) method; and 2) the ground conductivity model, composed of ground response functions inferred from magnetotelluric (MT) surveys. These two components are combined to calculate geoelectric fields over CONUS at a resolution of half a degree. There are a number of efforts in progress to validate and improve the NOAA-USGS geoelectric model: 1) analysis of the uncertainties associated with the geographical distribution of magnetic observatories used for the geoelectric calculations; 2) comparison of the modeled geomagnetic and geoelectric fields to measurements obtained from MT surveys during major storms; and 3) comparison of geomagnetically induced current (GIC) estimates obtained using the estimated geoelectric fields to measurements taken at power distribution systems. This presentation will cover the results from these activities and discuss how they will contribute to improving the geoelectric product by quantifying the uncertainties and errors, informing about the necessity of incorporating more magnetic stations, and determining the importance of these geoelectric models in assisting the power sector to build resilience to geomagnetic events.

Author(s): Enrico Camporeale, Andong Hu, Greg Lucas, Thomas Berger, Jennifer Knuth

University of Colorado; University of Colorado; University of Colorado; University of Colorado; University of Colorado

Abstract: We present a new model that is capable to forecast the ground (horizontal) electric field up to one hour in advance.  The model,called LiveWire, is part of the suite of forecasting models developed at the University of Colorado Deep Learning Lab an deployed in real-time on the SWxTREC (Space Weather Technology Research Education Center) staging platform: https://swx-trec.com/
We emphasize that so far this is the only product that can forecast in real time the ground electric field induced by geomagnetic variations. As a proof of principle we have initially developed the model for the site of the Boulder magnetometer station. An extension to the full continental US is planned.

Author(s): Andreas Johlander, Sven Molenkamp, Lisa Rosenqvist, Andrew Dimmock, Johan Setreus, Vanina Lanabere

Swedish Defence Research Agency; Swedish Defence Research Agency; Swedish Defence Research Agency; Swedish institute of Space Physics; Svenska Kraftnät; Sweish Institute of Space Physics

Abstract: The dynamic behaviour of the Sun and its interaction with the magnetosphere and ionosphere of Earth can cause rapid variations in the geomagnetic field at ground level giving rise to geomagnetically induced currents (GICs) flowing in long grounded conductors. The most severe impacts of GICs are potential power grid disruptions during intense space weather events.  In extreme cases, this can cause widespread power blackouts. Thus, it is important to investigate GICs in the power grid to understand the impacts in order to improve predictions and develop appropriate mitigation measures. In order to succeed with this on a larger scale a close collaboration between the scientific community and power grid operators is required.
A comprehensive list of disturbances reported in the Swedish power grid between 1999 and 2023 is evaluated in collaboration with the Swedish authority responsible for the electrical transmission system, Svenska Kraftnät. By using a recently developed regional modelling capability of geoelectric fields in Sweden together with a simplified yet representative equivalent circuit model of the Swedish national power grid the resulting GICs in all the earthing nodes of the network is calculated. The calculated GICs are cross-correlated with the power grid disturbances to determine which of these events may have been caused by space weather. By disregarding events with known causes (thunder, fallen trees, equipment failures etc.) events associated with significant voltage deviations are identified as likely GIC related disturbances. While it is not possible to pinpoint the exact location of the impact in the grid or the absolute magnitude of the GICs, which are both dependent on the accuracy of the grid circuit model, the maximum modelled GICs overlap with several, previously uncategorized, disturbances. These results highlight the value of the unique collaboration between the scientific community and the power grid operator in Sweden.

Author(s): Rute Santos, Alexandra Pais, João Cardoso, Fernando Pinheiro, Joana Alves Ribeiro

CITEUC, LIBPhys-UC; CITEUC; LIBPhys-UC; CITEUC; CITEUC

Abstract: Geomagnetic storms induce electric currents in the conductive Earth and in grounded conducting infrastructures, known as Geomagnetically Induced Currents (GICs).
Realistic GIC estimations, in particular GICs through power transformers, require an accurate representation of the power grid model. Shield Wires (ShW) are cables used to protect transmission lines against atmospheric discharges, typically grounded at substations and, often, at each supporting pylon. Although ShW provide an additional path for GICs, this effect is often overlooked, and previous studies have yielded different conclusions. This study focuses on how GIC simulated values change due to introducing ShW in the circuit model.
In order to address this issue, we adapted the GEOMAGICA [1] algorithm to include the ShW equivalent circuits [2], and carried out GIC simulations for the entire Portuguese power grid. The simulations incorporated realistic grid parameters and considered both a uniform electric field and a time-varying electric field calculated based on a 3D conductivity model [3]. By using a uniform electric field, the impact of the change in the grid topology can be isolated. It was found that the results for a complex network cannot be straightforwardly interpreted using a single-line analytical model. By using a time-varying electric field induced by a geomagnetic storm, we still notice the dominant effect of the grid topology. Our results show that, in general, including ShW in GIC calculations reduces GICs in substation grounding resistors but increases them in transformer windings.[1] Bailey, R. L., Halbedl, T. S., Schattauer, I., Römer, A., Achleitner, G., Beggan, C. D., … & Leonhardt, R. (2017, June). Modelling geomagnetically induced currents in midlatitude Central Europe using a thin-sheet approach. In Annales Geophysicae (Vol. 35, No. 3, pp. 751-761). Copernicus GmbH.[2] Santos, R., Pais, M. A., Ribeiro, J. A., Cardoso, J., Perro, L., & Santos, A. (2022). Effect of shield wires on GICs: Equivalent resistance and induced voltage sources. International Journal of Electrical Power & Energy Systems, 143, 108487.[3] Baltazar‐Soares, P., Martínez‐Moreno, F. J., Alves Ribeiro, J., Monteiro Santos, F. A., Ribeiro, P., Pais, M. A., … & Pous, J. (2023). Crustal imaging of Portugal mainland using magnetotelluric data. Earth and Space Science, 10(7), e2022EA002732.

SWR5.2 Tue 5/11 17:30-18:30, room C2B – Sofia

Author(s): Hannah Grace Parry, Ian Mann, Darcy Cordell, Martyn Unsworth, Andy Kale, David Milling, Ryan MacMullin

University of Alberta; University of Alberta; University of Alberta; University of Alberta; University of Alberta; University of Alberta; AltaLink LP

Abstract: Driven by space weather, fluctuations in the Earth’s magnetic field and the associated geoelectric field can result in geomagnetically induced currents (GICs) in long, grounded conductive infrastructure such as transmission lines. GICs in the power network can lead to heating in the transformer cores causing physical damage to the cores, as well as system effects from voltage instability and, in the worst case, wide-scale blackout events. Factors which affect GICs can include the topology and connectivity of the power network, the conductivity structure of the Earth underlying the power grid, and the temporal and spatial variation of the geomagnetic disturbances (GMDs) driving the GICs. Here we showcase a new multi-disciplinary partnership of scientists and engineers from academia and industry focussing on the characterisation, modelling, and potential impacts of  GICs in Alberta, Canada within a real and simulated data-driven modelling framework. This partnership includes researchers from the University of Alberta, industry partners from the province’s two largest electric utility companies (AltaLink L.P, ATCO Electric), and the provincial independent system operator (Alberta Electric System Operator). We leverage two existing datasets in the province: the dense CARISMA magnetometer array to characterize GMDs, and >500 surface impedance measurements collected from previous magnetotelluric (MT) surveys to characterize the conductivity of the Earth. Preliminary results of this collaborative work show the validation of an Alberta-wide, data-driven DC-equivalent network model using both GIC data collected at transformer neutrals, and GIC in the transmission lines inferred using a differential magnetometer measurement (DMM) method. The model performs well at four of five substations with transformer neutral current monitors (correlation coefficients >0.5, performance parameter >0.15), but underestimates peak GIC values (e.g., by more than a factor of 2 at one substation), indicating it may underestimate overall network risk. We further investigate combinations of the power network configuration and geoelectric field polarization in different geological regions of the province to examine the geology and network connectivity conditions which lead to the largest GIC risk in the network. We verify the importance of both ground impedance spatial variations and the network configuration when identifying power network elements which are at higher risk to large GIC.

Author(s): Mark A. Clilverd, Criag J. Rodger, James B. Brundell, Daniel H. Mac Manus, Xinhu Feng, Victor Lo, Michael Dalzell, Johnny Malone-Leigh

British Antarctic Survey (UKRI-NERC), Cambridge, UK; Department of Physics, University of Otago, Dunedin, New Zealand; Department of Physics, University of Otago, Dunedin, New Zealand; Department of Physics, University of Otago, Dunedin, New Zealand; Department of Physics, University of Otago, Dunedin, New Zealand; Transpower New Zealand Limited, Wellington, New Zealand; Transpower New Zealand Limited, Wellington, New Zealand; Department of Physics, University of Otago, Dunedin, New Zealand

Abstract: Large geomagnetic storms are a space weather hazard to power transmission networks due to the effects of Geomagnetically Induced Currents (GICs). GIC can negatively impact power transmission systems through the generation of even-order current and voltage harmonics of the power transmission frequency (typically 50 or 60 Hz) due to half-cycle transformer saturation. Such harmonics can cause networks to become destabilized, leading to blackouts and damage to transformers. Even-order harmonics contributed to the blackout of the Québec power system in March 1989. The generation of even-order harmonics is a sign of a transformer operating outside of its design range and becoming saturated through stray magnetic flux in the transformer. This potentially leads to damaging levels of internal heating. As such, the presence of even-order harmonics can be a sign of transformers under stress.
Very low frequency (VLF) measurements made by a radiowave receiver located close to the Halfway Bush (HWB) substation in Dunedin, New Zealand have been shown to detect even-order harmonics generated during a large geomagnetic storm in September 2017.  However, after the removal of the single phase bank transformer T4 in November 2017 the observation of even-order harmonics at HWB appeared to become much less likely as the remaining three phase units are known to be much less susceptible to GIC. Subsequent storms have confirmed this, with very small harmonic levels observed following the decommissioning of HWB T4. However, the recent geomagnetic storm of 10-11 May 2024 produced the largest GIC levels ever recorded at HWB, and even-order harmonics were observed multiple times by the VLF receiver. In this talk I will discuss the observations of 50 Hz harmonic enhancements during the geomagnetic storm, and their association with high GIC levels.
This research is part of the New Zealand Solar Tsunamis programme.

Author(s): Denny M. Oliveira, Eftyhia Zesta, Sergio Vidal-Luengo

NASA/GSFC, United States; NASA/GSFC, United States; University of Colorado Boulder, United States

Abstract: The impact of interplanetary (IP) shocks on the Earth’s magnetosphere can greatly disturb the geomagnetic field and electric currents in the magnetosphere-ionosphere system. At high latitudes, the current systems most affected by the shocks are the auroral electrojet currents. These currents then generate ground geomagnetically induced currents (GICs) that couple with and are highly detrimental to ground artificial conductors including power transmission lines, oil/gas pipelines, railways, and submarine cables. Recent research has shown that the shock impact angle, the angle the shock normal vector performs with the Sun-Earth line, plays a major role in controlling the subsequent geomagnetic activity. More specifically, due to more symmetric magnetospheric compressions, nearly frontal shocks are usually more geoeffective than highly inclined shocks. In this study, we utilize a subset (332 events) of a shock list with more than 600 events to investigate, for the first time, shock impact angle effects on the subsequent GICs right after shock impact (compression effects) and several minutes after shock impact (substorm-like effects). We use GIC recordings from the Finnish natural gas pipeline performed near the Mäntsälä compression station in southern Finland. We find that GIC peaks (> 5 A) occurring after shock impacts are mostly caused by nearly frontal shocks and occur in the post-noon/dusk magnetic local time sector. These GIC peaks are presumably triggered by partial ring current intensifications in the dusk sector. On the other hand, more intense GIC peaks (> 20 A) generally occur several minutes after shock impacts and are located around the magnetic midnight terminator. These GIC peaks are most likely caused by intense energetic particle injections from the magnetotail which frequently occur during substorms. Our results demonstrate that GIC effects triggered by shocks, especially the nearly head-on ones, can be detrimental to ground conducting infrastructure over time. The results of this work are relevant to studies aiming at predicting GICs following solar wind driving under different levels of asymmetric solar wind forcing.

Validating modelled pipe to soil potentials and GICs in New Zealand’s gas pipelines, Tim Divett, Malcolm Ingham, Mark Sigley, Kristin Pratscher, Tanja Petersen, Wiebke Heise, Craig Rodger

An extreme value analysis approach to quantifying site-specific GIC risk for critical energy infrastructure, Joseph Eggington

Rapid geomagnetic variations during geomagnetic storms driven by high-speed streams and coronal mass ejections, Marcus N. Pedersen, Liisa Juusola, Heikki Vanhamäki, Anita Aikio, Ari Viljanen

Identification of geomagnetic disturbances and investigation of the ring current during the events, G.E. Bower, S. Imber, S.E. Milan, A. Schillings, A. Fleetham, J. Gjerloev

Posters

Posters I  Display Tue 5/11 – Wed 6/11, room C1A – Aeminium

Authors in attendance: Tue 5/11 10:15–11:30, 15:15-16:15; Wed 6/11 10:15–11:30

Author(s): Mirjam Kellinsalmi, Elena Marshalko, Ilja Honkonen, Liisa Juusola, Ari Viljanen

Finnish Meteorological Institute; Finnish Meteorological Institute; Finnish Meteorological Institute; Finnish Meteorological Institute; Finnish Meteorological Institute

Abstract: Geomagnetically induced currents (GIC) are one of the most studied and potentially hazardous form of space weather impacts. Finnish Meteorological Institute has a long history of GIC measurements and real-time GIC modeling, with products also being delivered to the European Space Agency. Our latest research focuses on GIC estimation during the extreme Halloween geomagnetic storm, which caused the strongest measured GIC at the Mäntsälä pipeline in Finland.

We use IMAGE magnetometer data and 1-dimensional (1D) and 3-dimensional (3D) ground conductivity models for calculating the geoelectric field during the Halloween storm. Then, we calculate GIC in a simplified model of the Finnish 400 kV power grid, contrasting the results obtained with the 1D and 3D methods. This investigation is crucial for assessing localized GIC risks across the Fennoscandian region, highlighting areas where the 1D and 3D models produce the largest differences.

In addition to presenting our preliminary findings, we show a brief comparison between the GIC of the Halloween storm and the 2024 Mother’s Day storm. This comparative analysis improves our understanding of regional vulnerabilities and the importance of model accuracy, ultimately contributing to better risk assessment and mitigation strategies for future geomagnetic events.

Author(s): Mikhail Kruglyakov, Craig J. Rodger, Daniel H. Mac Manus, John Malone-Leigh, Kristin Pratscher, Malcolm Ingham, Wiebke Heise, Tanja Peterson, Michael Dalzell, Aaron Hendry, James B. Brundell

Department of Physics, University of Otago; Department of Physics, University of Otago; Department of Physics, University of Otago; Department of Physics, University of Otago; Victoria University of Wellington; Victoria University of Wellington; GNS Science; GNS Science; Transpower New Zealand Limited; Department of Physics, University of Otago, British Antarctic Survey; Department of Physics, University of Otago

Abstract: The Earth’s magnetic field disturbances, like geomagnetic storms and magnetospheric substorms, generate geomagnetically induced currents (GICs) in technological systems like power grids. The GICs calculation is of practical interest since, in some cases, they can irreversibly damage the transformers or even cause power grid blackouts.
However, the proper GICs simulations are quite challenging as one should take into account many factors that affect the GICs behaviour such as: a) spatial and temporal behavior of the inducing magnetic field is different for the different events and regions; b) the GICs are induced by geoelectric field, that in turns, depends on the ground conductivity; c) the GICs are strongly dependent on power grid configuration. Another challenge is that the simulations should be validated and, therefore, the observations of GICs are also necessary at least during some events and in some locations.
In this presentation we show how these challenges are overcome or, at least, are tackled by the New Zealand Solar Tsunamis project. Using the newly installed grid of magnetic field observations called MANA (Magnetometer Array for New Zealand Aotearoa), new full three-dimensional conductivity model for the lower part of the South Island, based on the magnetotelluric surveys, multi-site transfer function approach, and the power-grid model, provided by Transpower New Zealand Limited, we performed and validated the simulations of GICs during the strongest geomagnetic events in recent years. The obtained results show the good agreement with observed GICs and confirm that each and every aforementioned “ingredient” is necessary for the accurate simulation.

Author(s): Belakhovsky Vladimir, Pilipenko Vjacheslav, Sakharov Yaroslav, Selivanov Vasiliy

Polar Geophysical Institute, Apatity, Russia; Institute of the Physics of the Earth RAS, Moscow, Russia; Polar Geophysical Institute, Apatity, Russia; Northern Energetics Research Center, Kola Scientific Center RAS

Abstract: It was analyzed cases with extreme values ​​of geomagnetic-induced currents (GICs) in power transmission lines (PTLs) on the Kola Peninsula and Karelia for 2012-2022. The GICs registration system was created by the Polar Geophysical Institute and Northern Energetics Research Center (KSC RAS) ​​and includes 5 stations, oriented mainly in the north-south direction. Registration of GICs has been carried out continuously since end of 2011, and by 2022 a “quasi-solar cycle” of GICs registration has formed, including 24-25 cycles of solar activity. GIC data were compared with data from PGI magnetometers at the Lovozero and Loparskaya observatories, and with data from magnetometers of the IMAGE network. Extreme values ​​of GIC and dB/dt were compared with the parameters of the solar wind and interplanetary magnetic field, and geomagnetic activity indices. An analysis of GIС during strong magnetic storms over 11 years of observations is presented: March 17-18, 2013 [1], June 28-29, 2023 [2], March 17-20, 2015, September 7-8, 2017, May 27-29, 2017, etc.
The GIC data from the Vykhodnoy auroral station (VKH) and the Kondopoga subauroral station (KND) were considered. According to the VKH station data, 85 cases were selected as extreme events when the GIC value exceeded 30 A. The analysis shows that in most cases (60%) extreme growth of GIC occurs during CME magnetic storms, several cases occurred even without magnetic storms (3%), the remaining cases are during CIR storms (37%). It is found a connection between the occurrence of extreme GIC events and the solar activity cycle. For example, in 2019 and 2020, during the years of minimum solar activity, no extreme cases were recorded. According to the KND station data, 23 extreme events were selected when the GIC value exceeded 10 A. According to the KND station, extreme GIC values ​​are observed in 87% of cases during CME storms and in 13% of cases during CIR storms.
Almost all of the extreme GIC events occur during negative values of the Bz-component of IMF. There is no distinct connection between GIC value and solar wind speed V, V*Bs (where Bs – south component of the Bz), Akasofu parameter. So the problem of GIC prediction can’t be solved by the prediction of the solar wind parameters.
At the same time, there is no clear connection between value of GIC and dB/dt. Sometimes lower values of dB/dt lead to the high values of GIC and vice versa. We suppose that it is important to pay attention for the local ionosphere current systems.
The greatest GIC values occur during substorms (negative magnetic bays associated with the development of the western electrojet). At the same time, the development of vortex current systems during a substorm (Pi3/Ps6 geomagnetic pulsations) can make a noticeable contribution to the growth of GIС for power lines oriented in the north-south direction. The Pc5 pulsations and SSC events lead to medium (~20 A) and low values of GIC.

Author(s): Tim Divett, Malcolm Ingham, Mark Sigley, Kristin Pratscher, Tanja Petersen, Wiebke Heise, Craig Rodger

Victoria University of Wellington, New Zealand; Victoria University of Wellington, New Zealand; Firstgas Ltd; Victoria University of Wellington, New Zealand; GNS Science New Zealand; GNS Science New Zealand; University of Otago, New Zealand

Abstract: During solar storms, the induced geoelectric fields at ground level can lead to geomagnetically induced currents (GICs) and elevated pipe to soil potentials (PSPs) on gas pipelines. Operators of these pipelines use cathodic protection to keep PSP between -0.85V and -1.2V. This prevents corrosion of the steel pipes and disbondment of the protective coating from the pipes. The gas pipeline network in the North Island of New Zealand is made up of 2523 km of steel pipes coating with a resistive coating. We have developed a model of this pipeline network to assess whether space weather is a hazard to these pipelines and if so, to what extent. We used the equivalent-pi transmission line method to represent the electrical characteristics of the pipeline. We worked with the New Zealand owner and operator of the pipeline network who provided pipeline shapefiles and estimates of the electrical properties of the pipelines to develop this model. We calculated electric fields for a recent large storm from the magnetic field observations at Eyrewell and magnetotelluric (MT) impedance tensors. We then calculated PSPs and GICs on the pipeline network from these electric fields using the nodal admittance matrix method. We have validated the modelled PSPs against measurements at several sites on the pipeline network. We see good agreement in the magnitude and timing of spikes in modelled PSP time series at most observation locations. In general, the largest modelled PSPs are at the ends of the pipelines. This agrees with the characteristic curves seen in simpler pipelines, with variations due to branchlines, parallel lines, and spatial variation in electric field. With this validated model we will be able to confidently explore severe space weather events on the whole network including regions without observations. Ultimately this will lead to a better understanding of the effect of space weather on the New Zealand pipeline network and an increased ability to protect this infrastructure from extreme solar storms in the future.

Author(s): Anna Wawrzaszek, Agnieszka Gil, Renata Modzelewska, Bruce T. Tsurutani, Roman Wawrzaszek

CBK PAN; CBK PAN & University of Siedlce; University of Siedlce; Retired; CBK PAN

Abstract: The Sun is a dynamic star, significantly affecting the Earth’s vicinity. Namely, solar activity leads to increased fluctuations in the geomagnetic field and the formation of strong ground electric fields (GEFs). One of the most important consequences of exceptional high levels of GEF is the occurrence of geomagnetically induced currents (GICs), which are particularly dangerous for electrical infrastructure and the increase number of grid failures. As we approach the peak of Solar Cycle 25, increased solar activity is expected, as we have experienced during the May 2024 event, the most powerful geomagnetic storm in twenty years, since Halloween Storm.
In the frame of this work, we focus on the strong geomagnetic storm event on 23–24 April 2023 performing systematic analysis of the changes of geoelectric field during the geomagnetic storm. More precisely, we collect geomagnetic measurements with 10 s sampling rates of IMAGE ground magnetometers distributed over 51.4-69.8 northern Europe. In the next step the GeoElectric Dynamic Mapping (GEDMap) procedure is applied to perform systematic computation of geoelectric fields and to reveal spatio-temporal evolution of magnitude and direction of GEF.

Author(s): Marcus N. Pedersen, Liisa Juusola, Heikki Vanhamäki, Anita Aikio, Ari Viljanen

University of Oulu; Finnish Meteorological Institute; University of Oulu; University of Oulu; Finnish Meteorological Institute

Abstract: The most harmful geomagnetically induced currents (GICs) recorded have all occurred during geomagnetic storms. Still we do not have a complete understanding of their occurrence during geomagnetic storms driven by different solar wind transients, such as high-speed streams/stream interaction regions (HSS/SIR) or interplanetary coronal mass ejection (ICME) sheaths and magnetic clouds (MC). We developed an automated algorithm to detect geomagnetic storms and storm phases, resulting in a catalog of 755 geomagnetic storms from January 1996 to June 2023 with the solar wind drivers. Using these geomagnetic storms and data from the IMAGE magnetometer network we statistically studied the occurrence of spikes in the time derivative of the horizontal component of the external magnetic field, dHext/dt, greater than 0.5 nT/s to map the GIC activity throughout storms driven by HSS/SIR, sheaths and MCs. It is found that spikes occur more often toward the end of the storm main phase for HSS/SIR and MC-driven storms, while sheaths have spikes throughout the entire main phase. During the main phase most spikes occur in the morning sector around 05 magnetic local time (MLT) and the extent in MLT is narrowest for MCs and widest for sheaths. However, spikes in the pre-midnight sector during the main and recovery phases are most prominent for HSS/SIR-driven storms. During the SSC, three MLT hotspots exist, the post-midnight at 04 MLT, pre-noon at 09 MLT and afternoon at 15 MLT. The pre-noon hotspot has the highest probability of spikes and the widest extent in magnetic latitude.

Author(s): Kristin Pratscher, Malcolm Ingham, Wiebke Heise, Ted Bertrand, Mikhail Kruglyakov, Daniel Mac Manus, Craig Rodger, Tim Divett, Micheal Dalzell

Victoria University of Wellington, Wellington, New Zealand; Victoria University of Wellington, Wellington, New Zealand; GNS Science, Lower Hutt, New Zealand; GNS Science, Lower Hutt, New Zealand; University of Otago, Dunedin, New Zealand; University of Otago, Dunedin, New Zealand; University of Otago, Dunedin, New Zealand; Victoria University of Wellington, Wellington, New Zealand; Transpower New Zealand Ltd., Wellington New Zealand

Abstract: A regional-scale magnetotelluric (MT) survey of 53 sites collected in 2022-2023 has provided
sufficient electric field coverage of the northernmost North Island of Aotearoa, New Zealand. These
data were collected as part of a nationwide funded research programme called “Solar Tsunamis”
and they broaden our understanding of geomagnetically induced currents (GIC) within a region
where no measured MT data previously existed. Together with legacy MT data, MT transfer
functions calculated across the entire North Island and are combined with local magnetic
observatory data to compute GIC in transformers owned by the nation’s grid operator, Transpower
New Zealand Ltd. MT-based results from recent storms whose intensity ranged across the G3-G5
NOAA Space Weather Scales are rendered as electric field maps and GIC storm simulation time
series. Storm simulations from recent geomagnetic activity reveal the largest GIC occurring in the
transformers located along a resistive band of basement rock in Northland.

Author(s): Antti Pulkkinen

NASA GSFC

Abstract: In this work, we describe an approach to characterize the ground response to geomagnetic storm drivers and recalculate the scaling factors that are used in the U.S. NERC TPL-007 geomagnetic disturbance (GMD) standard based on magnetotelluric (MT) survey measurements.
The new ground response scaling factors indicate a significantly wider range of ground responses from the one-dimensional model responses used in the original NERC geomagnetic disturbance standards framework. Futher, the region Mid-West west of the great lakes and north-East around New England and areas along the Appalachian mountains appear to be particularly exposed to the geoelectric field hazard under extreme space weather conditions. A more complete validation of MT data in GIC applications is warranted before usage of the presented results as a basis for possible updates to the NERC GMD standard.

Author(s): Lauren Orr, Sandra Chapman, Ryan McGranaghan

British Geological Survey; 1- Centre for Fusion, Space And Astrophysics, Physics Department, University of Warwick, UK 2-Department of Mathematics and Statistics, University of Tromso, Norway 3-International Space Science Institute, Bern, Switzerland; NASA Jet Propulsion Laboratory

Abstract: Since 2013 the US has been collecting geomagnetic disturbance (GMD) data from 100+ power grid monitors and now has data from 23 geomagnetic storms with Kp>7. As space weather observations continue to increase in quantity and quality, we require novel methods to analyse these increasingly complex datasets such as network science. Network theory is frequently employed to estimate the resilience of the physical power grid, and its robustness to the removal of transformers due to threats such as natural hazards and cyber-attacks but is currently not applied to GIC. By applying network theory to the measured US dataset, we can utilize known parameters to test for vulnerabilities to space weather in the power grid across varying spatial and temporal scales. The network is formed using methods of association between the GIC data at each transformer. The transformer monitors are the nodes of the network, and the links are defined as when the wavelet cross-correlation of the GIC is sufficiently high (1). The wavelet transform is used to localise the GIC response to the storm across time scales. While previous network science studies have focused on the physical topology of the power grid, our approach focuses on the dynamical response of the grid to GIC. The results show the same transformers near Washington DC and Milwaukee frequently appearing as the most highly connected to the network across multiple events. These supernodes could be crucial to providing resilience and/or forecasting of potential disturbance of the power grid in the event of extreme space weather.

Author(s): Malcolm Ingham

Victoria University of Wellington, New Zealand

Abstract: The geomagnetic storm of 10 to 13 May 2024 was the largest such event for around 20 years and provided the opportunity to study how the cathodic protection system on the New Zealand gas pipeline network responded to significant space weather. Analysis of monitoring data from over 30 locations on the network revealed several features. (1) At widely spaced locations, there were very large variations in the potential between the anode bed and the pipe which at time became negative. (2) At these, and other locations, there were times when the pipe became positive with respect to a nearby reference cell. (3) At some locations the level of cathodic protection was outside the desired limits for considerable lengths of time. (4) At times, at some locations the DC power supply in the rectifier reached its maximum output and the current output fell to zero. Understanding these effects provides a baseline for future estimation of the potential effects of an “extreme” geomagnetic storm.

Author(s): Leonie Pick, Aline Guimarães Carvalho, Jens Berdermann

German Aerospace Center (DLR), Institute for Solar-Terrestrial Physics; German Aerospace Center (DLR), Institute for Solar-Terrestrial Physics; German Aerospace Center (DLR), Institute for Solar-Terrestrial Physics

Abstract: The current transition of solar cycle (SC) 25 into maximum phase provides an apt opportunity to investigate the impact of space weather on critical infrastructure, particularly in subauroral regions. This contribution focuses on the modeling of Geomagnetically Induced Currents (GICs) in the German high-voltage transmission grid (380kV) for recent geomagnetic storms of SC 25.
The modeling rests on geomagnetic disturbance maps deduced from INTERMAGNET observatory data which is combined with 3-D surface impedance tensors extracted from a dedicated conductivity model to give the induced geoelectric field in the period range ~10-10000s. The latter then interfaces with our transmission grid model in the form of additional voltage sources placed in power lines connecting grounded transformers to drive GICs.
Among the modeled events are the 23-24 April 2023 geomagnetic storm, for which we compare our results to direct GIC measurements from a substation in northwestern Germany, and the severe 10-12 May 2024 storm. We investigate the obtained GIC amplitudes across the country, incentivizing further direct GIC monitoring in areas of increased GIC risk.

Author(s): G.E. Bower, S. Imber, S.E. Milan, A. Schillings, A. Fleetham, J. Gjerloev

University of Leicester; University of Leicester; University of Leicester; Umeå University; University of Leicester; Johns Hopkins University Applied Physics Laboratory

Abstract: Geomagnetic disturbances (GMDs) are rapid changes in the magnetic field that can cause electric currents to be induced at the surface of Earth. These geomagnetically induced current (GICs) can cause damage to infrastructure such as pipelines and power grids. A detection algorithm has been developed to identify rapid changes in 10 second averaged magnetometer data. This higher resolution data is important in capturing the most rapid changes associated with extreme GIC events. It is necessary to distinguish between sudden changes which are genuine and which are caused by instrumental effects, so the algorithm provides a quality flag for each change, categorising it as good or doubtful. The algorithm has been used on an array of ground-based SuperMAG magnetometers for the years 2010 to 2022 creating a new global list of GMDs.
Recent studies have shown that there are two main populations of GMDs, one in the pre-midnight sector and one in the dawn sector. The Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE), is used to place the observed GMDs in the context of the global pattern of magnetosphere-ionosphere field-aligned currents (FACs). The dawn sector population of GMDs is found to lie near the boundary between the region 1 and region 2 FACs, while the pre-midnight sector population is found to occur poleward of the FAC boundary on region 1 upward FACs.
The cause of the pre-midnight GMDs has previously been related to the substorm current wedge. The dawn GMDs however have been suggested to be related to omega bands or Kelvin-Helmholtz activity.  Recently the dawn GMDs have been found to occur during multiple intensification events, which are related to rapid changes in the AL index with little change in the size of the polar cap. Previously multiple intensification events had only been identified for 2010. We adapt the SOPHIE substorm algorithm to identify more instances of multiple intensifications. Recent models suggest that the formation of a ‘dawnside current wedge’ (DCW) during the main phase of geomagnetic storms could lead to dawn sector GMDs. Using the new list of global GMDs we investigate their relationship to local time measurements of the magnetic field at low latitudes using the SuperMAG SMR local time indices (SMR-LT). During multiple intensification events the dawn sector magnetic field (SMR06) is typically higher than the dusk sector (SMR18), which is indicative of a DCW. Statistical analysis of the SMR-LT values during the dawn and pre-midnight GMD shows that the dawn GMD occur when the SMR06-SMR18 is largest and thus when a DCW is present.

Author(s): Joseph Eggington

EDF R&D UK

Abstract: Geomagnetically induced currents (GICs) could pose a risk to critical high voltage (HV) energy infrastructure via damage to transformers. EDF R&D UK carries out research into the potential impacts of GICs for EDF’s main HV transformers, including evaluation of extremely rare scenarios (up to 1-in-10,000-years) far beyond observed historical geomagnetic storms. Typically, past studies have estimated extreme GICs in power grids by simulating modern storms and scaling values equally across the network, e.g. based on geomagnetic indices. However, when the focus is on extreme GICs at specific grid nodes, the complex relationship between global indices and local geomagnetic activity, as well as the importance of local geology and network topology, introduces significant uncertainty.
Here we present a more statistically rigorous approach based on extreme value analysis (EVA), which is widely implemented for assessing risks from natural hazards. This uses statistical distributions of peak GIC during historical storms, unique to each node in the grid, to extrapolate to extreme levels. To achieve this, we have generated a dataset of GIC simulations in the UK and France transmission networks, covering a large number of storms over the last ~40 years. We present statistics from this dataset and show how the GIC at a given site cannot easily be predicted just based on storm magnitude, with each site showing unique variation. Using specific grid nodes as an example, we demonstrate the use of EVA to determine GIC return levels for a Carrington-level event and beyond, and show the large differences compared with predictions from a simple linear scaling based on indices. Our results highlight the need to consider the unique nature of each storm, and the local factors determining the GIC, to accurately characterise site-specific risk.

Author(s): Karen. V. Espinosa, Antonio L. Padilha, Livia R. Alves

National Institute for Space Research (INPE); National Observatory (ON); National Institute for Space Research (INPE)

Abstract: Modeling geoelectric fields is crucial for assessing geomagnetically induced risks in grounded systems triggered by space weather events, such as geomagnetic storms.  These risks derive from the coupling of multiple non-stationary and transient processes, related to variations in the geomagnetic field observed on the Earth’s surface, alongside stationary and relatively permanent processes, such as the distribution of electrical conductivity within the Earth. Accurate determination of geoelectric fields is one of the most critical objectives for monitoring and evaluating risks associated to Geomagnetically Induced Currents (GICs). This study focusses on the north-northeast Brazilian sector, influenced by the equatorial electrojet current system. The main objective is to quantify the contribution of permanent processes (subsurface impedance), periodic processes (the Equatorial Electrojet), and transient processes in amplifying geoelectric field amplitudes and potentially contributing to GIC amplifications. We conducted a regional study using geomagnetic field data from a temporary array settled in the equatorial region, arranged along three profiles nearly perpendicular to the dip equator. The study aims to identify trending, seasonal and residual components within geoelectric field time series under both quiet and disturbed geomagnetic conditions. Geomagnetic data were convolved with 3-D Magnetotelluric (MT) impedances derived from forward calculation of an Earth conductivity model obtained from a combined GDS-MT inversion to obtain geoelectric fields. By isolating the influence of the Equatorial Electrojet (EEJ), our findings suggest a joined effect derived from the resistive structure in the subsurface and the non-static electrojet current system. This study is the first attempt to break down geoelectric field time series into trend, seasonality, and residuals components. This approach aims to employ separate models for each component to produce individual forecasts. These forecasts could serve as a basis for understanding and predicting variations in geoelectric field amplitudes. Subsequently, integrating these individual forecasts would enable the creation of a comprehensive forecast model.

Author(s): Alexander Fröhlich, Philipp Schachinger, Herwig Renner

Graz University of Technology, Institute of Electrical Power Systems; Austrian Power Grid AG; Graz University of Technology, Institute of Electrical Power Systems

Abstract: The Mother’s Day solar storm served as a key investigation into the resilience of the Austrian transmission grid to geomagnetic disturbances. This paper addresses the effects of this solar event, focusing on the geomagnetically induced peak currents (GICs) measured in different substations in Austria. The analysis shows how the resilience of the electricity grid was put to the test by these extreme conditions and highlights key areas for improvement in the future.
GIC measurements at the transformer neutral points started in Austria in 2014 and have been continuously improved and expanded. During the Mother’s Day solar storm, seven out of nine transformer neutral point measurement stations were in operation, providing important data and insights into the effects of geomagnetic disturbances on the power grid.
During the solar storm, a transformer in southern Austria was subjected to the strongest geomagnetically induced currents (GICs) ever recorded in the region. This transformer is also equipped with a Power Quality Analyzer for monitoring harmonic distortions. Additionally, a Power Quality measurement is installed at a second transformer recorded similar current and voltage harmonics. This monitoring also enabled an assessment of a possible increase in the transformer’s reactive power demand. Based on the measurements, this work analyses and validates the voltage and current harmonics occurring at two power transformers in the Austrian transmission grid.
Despite the intensity of the solar event, no significant disturbances were reported in the grid. The grid operator did not detect any voltage issues or other anomalies. However, there are no measurements on permanent saturation, and thus, data on continuous effects are unavailable.
In summary, the solar storm on Mother’s Day highlighted the impacts of the Austrian transmission grid on geomagnetic disturbances. Although the currents were the highest ever recorded, the impact on the Austrian transmission grid was low and not recognized by the grid operators. Nevertheless, saturation occurred in transformers and harmonic distortions were measured.

Author(s): Andrew P. Dimmock, Vanina Lanabere, Andreas Johlander, Lisa Rosenqvist, Emiliya Yordanova, Stephan Buchert, Sven Molenkamp

Swedish Institute of Space Physics, Uppsala, Sweden; Swedish Institute of Space Physics, Uppsala, Sweden; Swedish Defence Research Agency, Stockholm, Sweden; Swedish Defence Research Agency, Stockholm, Sweden; Swedish Institute of Space Physics, Uppsala, Sweden; Swedish Institute of Space Physics, Uppsala, Sweden; Swedish Defence Research Agency, Stockholm, Sweden

Abstract: Geomagnetically Induced Currents are unwanted currents that flow in large ground-based conductive infrastructure and are a significant threat to bulk power grids. In Sweden, there has been a record of disturbances connected to geomagnetically induced currents, the most documented was a blackout in Malmö, a city in southern Sweden on 30 October 2003. However, on 24 April 2023, there was a failure in a power line in Bandsjö around the time of enhanced space weather. In this paper, we investigate this event by studying the solar wind properties, and geomagnetic disturbances at that time. We conclude that the failure was most likely caused by a strong substorm in the morning sector around the time of a high-pressure sub-structure within the interplanetary coronal mass ejection cloud. This was preceded by two hours of strong southward IMF that would have played a significant role. Other Fennoscandian magnetometers also show that the geomagnetic impact from the substorm was highly spatially structured and strongest in Norway.

Author(s): Venera Dobrica, Crisan Demetrescu, Cristiana Stefan

Institute of Geodynamics, Romanian Academy; Institute of Geodynamics, Romanian Academy; Institute of Geodynamics, Romanian Academy

Abstract: According to various authors, the geomagnetic storms with Dst less than -500 nT are considered superstorms, the well-known one being the superstorm of March 13-14, 1989, with Dst = -589 nT. In the present study, the space-age magnetic superstorms (March 1989, November 2003, May 2024) will be investigated from the point of view of the associated hazard, described in terms of the electric field at the surface of the Earth, which in turn can result in geomagnetically induced currents (GICs), on the Romanian territory. The surface electric field, produced by the variable magnetic field of geomagnetic storms, is determined on the basis of records from the Surlari geomagnetic observatory (SUA) and information on the ground electrical conductivity inferred from MT studies. We show that the amplitude of geoelectric field depends on the morphology rather than the amplitude of the disturbance, and is three times higher in case of March 1989 than in case of the other superstorms. The geographical distribution of the amplitude of the geoelectric field vector is represented on the territory of Romania, constituting the geoelectric hazard map at the country scale.

Author(s): João Fernandes, Rute Santos, João Cardoso, Alexandra Pais

LIBPhys-UC; CITEUC, LIBPhys-UC; LIBPhys-UC; CITEUC

Abstract: Geomagnetic Storms are strong fluctuations in the geomagnetic field, which result from interactions between the Earth’s magnetosphere and the energetic solar wind. During these events, electric fields are induced in the Earth’s subsurface and in man-made grounded conductive infrastructure, leading to the flow of electric currents known as Geomagnetically Induced Currents (GICs) in these systems. They can pose a significant threat to electrical transmission networks due to their potential to cause transformer saturation and subsequent power grid failures.
The proposed system, designated as ENERGIC, monitors electric currents in the neutral cable of a power transformer at a substation. It employs a Hall effect sensor and a data acquisition board to measure and record these currents. The processing is performed by a Raspberry Pi, allowing for Python scripting and the use of Python libraries that support the development of the software required for the measurement tasks. The data is stored continuously in both a local and a remote InfluxDB time-series database, and it can be interactively visualized on a customizable dashboard using the Grafana web interface. An Uninterruptible Power Supply (UPS) protects the system against unexpected shutdowns caused by power outages and/or glitches in the electrical substation and monitors power related metrics of the system such as its power usage and battery level.
This system builds upon a previous generation of the measurement system, addressing some of the limitations that were observed. Ultimately, the system presented here offers increased sensitivity to GICs, enhanced mechanical and galvanic isolation, improved data access for real-time telemetry visualization, and better power autonomy with integrated anomaly alerts.
The installation of ENERGIC is expected to take place at the Paraimo substation near Coimbra by the end of the summer. As the solar cycle 25 approaches its peak, heightened solar activity increases the probability of geomagnetic storms and consequent GIC events in power systems. This upcoming phase presents a valuable opportunity to validate our simulations with measurements, as GIC data is expected to become more readily available.