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Risks of solar storms may be underestimated, warn researchers
The effects of extreme space weather may be larger than previously thought, research in the journal Nature reveals. The paper, titled "Regression to the mean can explain saturation of geomagnetic storms," is led by Dr. Nithin Sivadas of NASA's Goddard Space Flight Center and co-authored by Dr. Maria Walach from Lancaster University.
Space weather—caused by fluctuating electric fields in Earth's magnetic field and upper atmosphere—can affect technologies on and around Earth in several ways. Extreme geomagnetic storms are among the less frequent but more severe forms of space weather.
Extreme geomagnetic storms are temporary disturbances in the plasma and magnetic field around Earth that can disrupt global satellite communications, cause extensive power outages and affect how much radiation astronauts and pilots are exposed to.
An upper limit in doubt
For decades, scientists have thought there is an upper limit to how Earth responds to solar storms. Electric currents in Earth's upper atmosphere are widely understood to reach an upper limit as solar wind strength increases.
But new research suggests the upper limit is an illusion resulting from uncertainty in measurements of solar wind strength, as the true value regresses toward the mean. If so, this means solar storms could have far worse effects on our technology than previously thought.
Walach said, "Our planet's magnetic field does a really great job of protecting us against many space weather effects, and so they often just show up as glitches or beautiful aurora. There are, however, extreme cases where satellites unexpectedly fall back to Earth, or we lose communication and GPS signals."
Where the measurements mislead
The solar wind is a never-ending stream of hot gases flowing from the sun that can strengthen during solar eruptions. Observations have suggested that as the solar wind strengthens, electric currents in Earth's upper atmosphere—which can affect satellites, communications and navigation signals—increase to a certain point but then, on average, level off.
The team says this apparent limit is merely an effect of uncertainties in solar wind measurements.
They claim the issue is that most solar wind measurements of extreme events are taken by spacecraft at Lagrange point 1, which is a million miles (1.6 million kilometers) closer to the sun than Earth. Hence, the solar wind that strikes Earth is likely weaker due to a regression-to-the-mean effect. Averaging observations from many events makes it look like strong solar winds do not produce equally strong currents because, on average, weaker solar winds arrive at Earth.
Evidence closer to Earth
The team found evidence from more than a million solar wind measurements taken by Earth-orbiting NASA spacecraft very close to our planet. Analysis of these observations showed a direct relationship between the strength of the solar wind and the currents in the upper atmosphere, suggesting there is no upper limit. Rather, Earth's response will continue to increase along with solar wind strength, and impacts on technology can increase as well.
Walach said, "If there is no upper limit to our planet's response to the solar wind, modeling for extreme cases needs to take this into account, and we should be vigilant of space weather effects. Fortunately, these very extreme cases are rare, but this also means we have limited data to work with, and only time will tell what happens at a very extreme, one-in-a-thousand-year kind of event."
The lead author, Sivadas, said, "We usually assume the truth may be around its measurement. But probability theory says it leans one way. That's why space weather risks appear underestimated."
Publication details
Nithin Sivadas, Regression to the mean can explain saturation of geomagnetic storms, Nature (2026). DOI: 10.1038/s41586-026-10757-4. www.nature.com/articles/s41586-026-10757-4
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Citation: Risks of solar storms may be underestimated, warn researchers (2026, July 15) retrieved 16 July 2026 from https://phys.org/news/2026-07-solar-storms-underestimated.html
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