The most powerful solar storms to strike Earth may pack a bigger punch than scientists realized, according to a new study that suggests the impacts of extreme space weather have been underestimated.

Researchers found evidence that the apparent upper limit on Earth's response to the strongest solar storms may be an artifact of how solar wind has been measured rather than a true physical ceiling. If confirmed, the findings suggest that rare "once-in-a-thousand-year" geomagnetic storms could have a greater impact on modern technology than current estimates indicate, according to a statement.

"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," Maria Walach, co-author of the study from Lancaster University, said in the statement. "There are however extreme cases."

Solar storms occur when eruptions from the sun, such as coronal mass ejections and solar flares, send clouds of charged particles hurtling toward Earth. While they can produce spectacular auroras, they can also disrupt satellites, GPS, radio communications and power grids.

History has shown the damage even less extreme storms can cause. The 1859 Carrington Event, the strongest geomagnetic storm on record, disrupted telegraph systems around the world and pushed auroras from their usual high-latitude skies near the Arctic and Antarctic to locations as far south as the tropics. Another powerful storm in 1989 collapsed Quebec's power grid, leaving millions without electricity, while the 2003 "Halloween storms" disrupted satellites, GPS and radio communications.

While the study doesn't suggest that an unprecedented solar storm is imminent, it argues that scientists may need to rethink how they estimate the severity of the rarest events — an increasingly important challenge as modern society grows more dependent on satellites and other vulnerable technologies.

The researchers traced the apparent upper limit to where most solar wind measurements are collected. Many observations of extreme events come from spacecraft near the Sun-Earth Lagrange Point 1 (L1), about 1 million miles (1.5 million kilometers) upstream of Earth. Because the strongest solar wind tends to weaken somewhat before reaching Earth, comparing L1 measurements with conditions at our planet can make it appear that Earth's upper atmosphere stops responding to increasingly intense solar wind, even when it does not.

To test that idea, the team analyzed more than one million solar wind measurements collected by NASA spacecraft orbiting much closer to Earth, where the solar wind directly interacts with our planet's magnetic field. Those observations showed that electrical currents flowing through Earth's upper atmosphere continued to increase alongside stronger solar wind, with no sign of the previously assumed upper limit. The results suggest that exceptionally powerful solar storms could generate stronger geomagnetic disturbances — and greater impacts on satellites, communications systems and power grids — than earlier estimates predicted.

"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 the very extreme one-in-a-thousand-year kind of event," Walach said in the statement.

The study comes as the sun remains near the peak of its roughly 11-year solar cycle, known as solar maximum, when sunspots, solar flares and coronal mass ejections become more frequent. During the current cycle, strong geomagnetic storms have repeatedly sent auroras far beyond their usual polar skies.

In May 2024, the strongest geomagnetic storm in more than two decades illuminated skies across much of the United States and Europe while causing intermittent disruptions to high-frequency radio communications, GPS-guided equipment and some satellite operations. Although significant, that event was far less powerful than the Carrington Event — or the even rarer storms the new study suggests may be possible.

The findings were published July 15 in the journal Nature.

Fourth of July celebrations across the United States this weekend could be accompanied by light shows in the night skies, as a string of powerful solar eruptions appear set to strike Earth.

The sun has been especially hyperactive over the past few days — firing off 10 M-class solar flares over 24 hours that have been accompanied by multiple coronal mass ejections (CMEs), which are set to slam into Earth on July 3 and July 5.

CMEs are large, fast-moving clouds of magnetized plasma and solar radiation that occasionally get flung into space with solar flares when kinks in the sun's magnetic field snap. If CMEs smash into Earth, they cause disturbances in Earth's magnetic field, called geomagnetic storms, that can trigger partial radio blackouts and produce vibrant aurora displays farther away from Earth's magnetic poles than usual.

"Machine-Gun Sun! More than 5 storms on their way to Earth and 3 of them offer good chances for aurora views," Tamitha Skov, a space weather physicist at Millersville University of Pennsylvania, wrote in a July 2 post on the social platform X. "NOAA and NASA model predictions do not show all the storms yet (it's hard to keep up with the rapid-fire storm launches!) but the first should hit before noon July 3 UTC."

The CMEs are expected to give a glancing blow to our planet, creating conditions for a moderate (G2) geomagnetic storm, according to the National Oceanic and Atmospheric Administration's (NOAA) Space Weather Prediction Center. It's also possible that these storms will strengthen to become strong (G3), depending on how they interact with Earth's magnetic field.

Auroras resulting from G3-class geomagnetic storms are often visible in northern parts of Washington, Idaho, Montana, Wyoming, North Dakota, South Dakota, Minnesota, Wisconsin, Michigan, New York and Maine, according to NOAA. Skywatchers farther south in Oregon, Nebraska, Iowa, Illinois, Indiana, Ohio, Pennsylvania, Massachusetts, Connecticut, Rhode Island, Vermont and New Hampshire will also have a chance of catching the light show. In any case, skywatchers interested in seeing or photographing the auroras will need to get as far from artificial light sources as possible.

The weekend storms might not be the last activity we see from the sun in the coming days, as two gigantic sunspots currently pimpling its face are displaying "beta-gamma-delta" magnetic fields — the most tangled and unstable type. This means these sunspots harbor the potential to launch powerful X-class flares, according to spaceweather.com.

The last few years have seen a record number of powerful X-class flares explode from the sun's surface, hitting Earth with several major solar storms, including 2024's Mother's Day storm. This record comes partly from improvements to scientists' solar monitoring technologies, but also due to the sun reaching its 11-year peak in sunspot production, or solar maximum, in 2024.

Following this peak, the sun has now entered a period known as the "battle zone," a relatively understudied solar phase where instabilities across our star's newly flipped magnetic field ramp up the production of solar holes, gigantic, highly-tangled sunspots and subsequent geomagnetic storms.

The worst-case scenario for a solar storm is a superstorm like the 1859 Carrington Event, which released roughly the same energy as 10 billion 1-megaton atomic bombs. After slamming into Earth, the powerful stream of solar particles set telegraph systems around the world on fire and caused auroras brighter than the light of the full moon to appear as far south as the Caribbean.

The Carrington Event unleashed a roughly X45 magnitude solar flare that remains a record, yet it's likely far from the worst the sun can muster — with ancient tree rings harboring evidence of even more powerful blasts that occurred long before humans existed.