Study: Extreme geomagnetic storm impact may be twice as severe
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A new study in Nature finds that the saturation of geomagnetic activity with solar wind strength is due to a regression to the mean effect, implying extreme storms could be twice as powerful as previously estimated. The research, led by Dr. Nithin Sivadas of NASA's Goddard Space Flight Center and co-authored by Dr. Maria Walach of Lancaster University, challenges current space weather models. The findings suggest that historical storm intensity may have been systematically underestimated.
The Regression Effect
The study, published in Nature on July 15, 2026, demonstrates that the observed saturation of geomagnetic storms — where storm intensity plateaus despite increasing solar wind strength — is a statistical artifact of regression to the mean. Lead author Dr. Nithin Sivadas of NASA Goddard and co-author Dr. Maria Walach of Lancaster University analyzed decades of solar wind and geomagnetic index data. They found that when solar wind driving is weak, random fluctuations can cause overestimation of storm intensity, while strong driving leads to underestimation, creating an artificial saturation curve.
Implications for Risk Assessment
Correcting for this regression effect reveals that extreme geomagnetic storms, such as the 1859 Carrington Event, may have been twice as intense as previously modeled. According to the researchers, this means that worst-case scenario storms could produce ground-induced currents strong enough to damage power grids and satellites at levels not accounted for in current infrastructure planning. The findings suggest that existing space weather forecasting models may underestimate the potential impact of rare, high-intensity events.
What's Next
The research team plans to refine their statistical model and apply it to historical storm data to produce revised intensity estimates. It remains unclear how quickly space weather agencies will update their hazard models to incorporate the new findings.
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Study: Extreme geomagnetic storm impact may be twice as severe
