Extreme solar storms can hit Earth harder than thought

Extreme solar storms can hit Earth harder than thought

Scientists have greatly underestimated the impact an extreme solar storm can have on Earth, according to new research.

A new way to account for uncertainty in solar wind measurements could help communication and power system operators better prepare for disruptions caused by major solar storms.

Space weather experts have maintained that Earth's magnetic environment seems to have a limit on how much the solar wind, a stream of charged particles from the sun, can disturb it.

Research published July 15 in Nature, however, shows that Earth's magnetic field does not appear to have such a limit. Disturbances at the surface and in near-Earth space could therefore be twice as strong as scientists have estimated for a major solar storm.

Geomagnetic storms are rated from G1 to G5, with G5 being the most severe.

Doğacan Öztürk, assistant professor of physics at the University of Alaska Fairbanks Geophysical Institute and UAF College of Natural Science and Mathematics, said current estimates can make a storm appear more severe than the solar wind conditions that actually caused it.

That means scientists may be underestimating how strongly Earth's magnetic field would respond to intense solar storms. What's considered a G5 storm today may not represent the greatest possible impacts.

"We are grossly underestimating our preparedness for it because we haven't accounted for uncertainties in how we measure solar storms," Öztürk said.

The finding means that satellites and other space-based systems, as well as power grids, communications and navigation systems, are at greater risk of damage from an extreme event than previously believed.

Öztürk is among the research paper's co-authors. Nithin Sivadas of NASA Goddard Space Flight Center and the Catholic University of America is the study's lead author.

"We measure solar wind far away from Earth, and it gets altered in random ways before reaching us," Sivadas said. "So what we measure is an uncertain estimate of what actually strikes our planet."

Scientists generally measure the solar wind at Lagrange Point 1, or L1, about 1.5 million kilometers (930,000 miles) from Earth toward the sun. Those measurements provide advance warning before the solar wind reaches Earth.

The great distance does come with a problem: The solar wind can change between L1 and Earth.

"It is well known that the solar wind slows down as it first encounters Earth's magnetic field at a region called the bow shock," Sivadas said.

Between there and Earth, turbulence and waves can change the solar wind in unpredictable ways, Sivadas said.

Past observations appeared to show that disturbances in Earth's magnetic environment reached a limit, or saturation point, during extreme solar wind conditions.

Sivadas and his colleagues found that the apparent saturation was an illusion caused by uncertainty in the measurements.

It turns out our observed magnetic disturbances may have occurred in response to weaker solar winds than scientists have assumed. A truly extreme solar storm could therefore produce a much stronger disturbance than current models predict.

That knowledge "challenges the foundation of existing physical theories of saturation and highlights the need to revisit and validate them," the authors write.

Scientists create scenarios for extreme storms that might occur only once in 100 years. They use those scenarios to estimate the effects on satellites, communications, navigation systems and power grids.

"These worst-case scenarios are widely used to set safety thresholds, which industries and even agencies can adopt to establish reliability standards," Öztürk said.

Öztürk said the research shows that scientists must account for uncertainty when interpreting measurements rather than treating each measurement as an exact representation of the conditions that actually reached Earth.

"Our current way of measuring does not really reflect the truth," she said.

ADDITIONAL CONTACTS: Doğacan Öztürk, [email protected]; Nithin Sivadas, [email protected]

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