New Study Reveals Prolonged Geomagnetic Storms Pose Unseen Risks to Power Grids
Geomagnetically induced currents (GICs) can cause prolonged stress on power grids, according to a 2026 study published in *Space Weather*. The research highlights a 2015 geomagnetic storm in New Zealand that exposed gaps in existing monitoring tools, raising concerns about grid vulnerabilities.
The 2015 Geomagnetic Storm: A Wake-Up Call for Grid Operators
A severe geomagnetic storm in June 2015, rated G4 by the U.S. Space Weather Prediction Centre, disrupted New Zealand’s power grid in an unexpected way. Unlike typical storms that cause brief current spikes, this event generated sustained GICs lasting 90 minutes, with currents reaching 20 amperes. While the magnitude seemed low, the duration posed a unique risk, as prolonged exposure can saturate transformer cores and lead to overheating.
Transpower New Zealand provided critical data for the study. Researchers from the University of Gothenburg, Sweden, traced the anomaly to a “mid-latitude ionospheric current wedge,” a phenomenon where part of the Earth’s ring current diverted into the ionosphere. This diversion altered traditional measurements, making it harder to predict grid impacts.
Why Current Monitoring Tools Fall Short
Scientists typically rely on the rate of change of Earth’s horizontal magnetic field (H’) to estimate GICs. However, during the 2015 storm, H’ readings failed to correlate with actual grid currents. The ionospheric wedge distorted key parameters, revealing a critical gap in existing models.
Local Variations Highlight Grid Vulnerabilities
The study found that GICs varied significantly even over short distances. Two substations in New Zealand’s South Island, just 5 km apart, recorded differing current levels. This suggests that local ground conductivity and grid design play a major role in how storms affect power infrastructure.
The researchers emphasized that protective measures must consider both sudden spikes and prolonged currents, rather than focusing solely on peak values.
FAQ: Understanding Geomagnetic Storms and Power Grid Risks
What are geomagnetically induced currents (GICs)?
GICs are electric currents generated by changes in Earth’s magnetic field during geomagnetic storms. They can flow through power grids, damaging transformers and causing outages.
Why was the 2015 New Zealand storm unusual?
The storm produced prolonged GICs lasting 90 minutes, unlike typical events that cause brief spikes. This challenged existing monitoring methods and highlighted new risks.
How can power grids be protected?
Local geology and grid layout also influence vulnerability.
Stay Informed: Explore More on Space Weather and Energy Resilience
For deeper insights into solar activity and its impact on infrastructure, read our article on space weather forecasting techniques. To learn how other countries are preparing for geomagnetic risks, visit global energy resilience strategies.
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