Extreme Solar Storm Hit Earth During Sun's Quiet Period 10,000 Years Ago

An extreme solar storm struck the Earth around 10,000 years ago during what was supposed to be one of the sun's quiet periods, according to a study.

The sun produces a powerful magnetic field which varies over the course of roughly 11-year-long cycles. At the end of these periods, the polarity of the magnetic field flips, meaning that the north and south poles switch.

Scientists refer to the end of this cycle as a solar minimum, which is generally thought to be the period when the sun is least active. The middle of the cycle—the solar maximum—tends to be a period of high activity.

During solar maximums, sunspots increase in frequency on our star. These are temporary dark patches that appear in the sun's photosphere, or outer shell. Other solar phenomena, such as solar storms, also increase during solar maximums.

These phenomena emit vast amounts of energy that can even affect the Earth. For example, solar storms can sometimes disrupt communication systems and electronic grids on our planet if they are powerful enough.

But while solar storms are thought to be more likely to occur during an active phase of the sun, a study published in the journal Nature Communications demonstrates that this might not always be the case for very large storms.

In the study, an international team of scientists—led by experts from Lund University in Sweden—analyzed ice core from Greenland and Antarctica.

This analysis revealed evidence of a previously unknown, extreme solar storm that hit the Earth 9,125 years ago. The researchers said that this storm occurred during one of the sun's "passive phases."

During solar storms, the sun expels large quantities of energetic particles that can react with substances in the Earth's atmosphere and produce radioactive isotopes, such as beryllium-10 and chlorine-36.

When the researchers analyzed the ice cores from Greenland and Antarctica, they detected large peaks of these isotopes, providing evidence of a powerful storm during one of the sun's quiet periods.

"This is time consuming and expensive analytical work. Therefore, we were pleasantly surprised when we found such a peak, indicating a hitherto unknown giant solar storm in connection with low solar activity," geology researcher Raimund Muscheler said in a Lund University statement.

If a solar storm of this magnitude occurred today, it could have serious consequences, according to the researchers, although the impact to our planet would be hard to predict.

"There could be radiation damage to satellites and it would pose a danger to space and air travel," Muscheler told Newsweek.

"Usually such high-energy events are linked to geomagnetic storms that could knock out power grids. Similarly communication systems could fail. I think we need more research to determine how such an event could affect our technological infrastructure."

Muscheler said these kinds of enormous storms are currently not sufficiently included in risk assessments.

"It is of the utmost importance to analyze what these events could mean for today's technology and how we can protect ourselves," Muscheler said in the statement.

The researchers also said in the study that identifying whether a relationship exists between solar activity and the occurrence of extreme solar storm events is "fundamental" for the planning of space missions, in order to minimize the risks to spacecraft and the health of astronauts.

Update 2/4/22, 7:52 a.m. ET: This article was updated to include additional comments from Raimund Muscheler.

Illustration of a solar storm
A stock illustration of a solar storm striking the Earth. An extreme solar storm struck the Earth around 10,000 years ago during what was supposed to be one of the sun’s quiet periods, according to a study. iStock