Scientists say a 'once-in-a-thousand-year' solar storm could hit harder than we model

A new study in Nature (published July 15) challenges a core assumption space-weather researchers rely on: the idea of an upper limit on how hard Earth’s atmosphere responds to the most extreme solar wind. The researchers suggest that apparent “ceilings” could be artifacts of how solar wind has historically been measured. If that holds up, the rare “once-in-a-thousand-year” geomagnetic storms could create stronger disturbances and bigger real-world impacts on satellites, communications, and power grids than current estimates indicate.

To understand why this matters immediately, zoom in on the mismatch the team tested. Many extreme-event observations have come from spacecraft near the Sun-Earth Lagrange Point 1 (L1), about 1 million miles (1.5 million kilometers) upstream of Earth. The strongest solar wind tends to weaken somewhat before reaching Earth, so comparing L1 measurements with what happens at the planet can make it look like Earth’s upper atmosphere stops responding as solar wind gets more intense, even when it does not.

The researchers didn’t just theorize. They analyzed more than one million solar wind measurements taken by NASA spacecraft orbiting much closer to Earth, at a location where the solar wind directly interacts with Earth’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. Put plainly: the data suggest the “max” wasn’t a law of nature. It was a measurement boundary.

This is the kind of finding that turns down a dial board members and risk teams care about. Space weather is not just a science curiosity. Solar storms happen when eruptions from the sun such as coronal mass ejections and solar flares send clouds of charged particles toward Earth. The results can include spectacular auroras, but the operational footprint can be messy: disruptions to satellites, GPS, radio communications, and power grids. The historical record the study points to shows that even storms not at the “once-in-a-thousand-year” level have caused real damage.

The 1859 Carrington Event, described as the strongest geomagnetic storm on record, disrupted telegraph systems worldwide and pushed auroras from high-latitude skies near the Arctic and Antarctic down as far south as the tropics. In 1989, a powerful storm collapsed Quebec’s power grid, leaving millions without electricity. And in 2003, the “Halloween storms” disrupted satellites, GPS, and radio communications. Those examples are not the same as a modern tech stack versus 19th-century telegraphy, but they do underline the direction: the upper tail of solar activity can overwhelm infrastructure in ways that are hard to “paper over” with redundancy.

Importantly, the study does not claim that an unprecedented solar storm is imminent. Instead, it argues something more uncomfortable for planners: scientists may need to rethink how they estimate the severity of the rarest events. That becomes increasingly important because modern society is more dependent on satellites and other vulnerable technologies. The researchers also stress the practical problem created by rarity itself. Walach, co-author from Lancaster University, is quoted in the statement saying that these very extreme cases are rare, which means limited data to work with, and “only time will tell what happens” at the very extreme “one-in-a-thousand-year” level.

Now connect this to the regulatory and operational reality. When risk models rely on an assumed physical ceiling, the resulting planning ranges, insurance pricing, resilience spending, and operational contingency thresholds can all inherit that bias. That matters for regulators overseeing critical infrastructure resilience and for operators who have to translate scientific uncertainty into measurable controls. Even without naming a specific agency in the source, the implication is straightforward: if the rare tail is bigger than expected, the “acceptable” level of outage duration or communication degradation built into business continuity plans may be too optimistic.

Meanwhile, the timing is not random. The study comes as the sun remains near the peak of its roughly 11-year solar cycle, known as solar maximum. Sunspots, solar flares, and coronal mass ejections become more frequent then. 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. That event was far less powerful than the Carrington Event or the even rarer storms the new study suggests may be possible.

So what should executives and boards take from this? The headline is not “prepare for a new apocalypse next week.” It’s “your worst-case might be underestimated because the evidence used to build it may have been filtered through where instruments were placed.” If the apparent upper limit was partly a measurement artifact, then the rarest tail events deserve a second look in technology resilience planning, stakeholder communication, and capital allocation for systems that keep time, coordinate logistics, and move power. For leaders across satellite operations, utilities, and any organization that leans on GPS or radio communications, the strategic stake is simple: in the extremes, small modeling errors can become expensive operational surprises.