Evidence of extreme solar storm found in ice cores | Polarjournal
The sun determines the space weather. Solar flares or coronal mass ejections have a wide variety of effects on Earth or in near-Earth space, from auroras to disruption of communications systems. Illustration: NASA

About 9,200 years ago, a gigantic spectacle may have taken place in the skies above the Arctic and Antarctic. Analyzing ice cores from Greenland and Antarctica, an international team of researchers led by Lund University in Sweden, found that an extreme solar storm occurred at the time, which certainly caused the auroras to dance extensively and colorfully. What makes this storm special is that it occurred during a quiet phase of the sun.

This historic solar storm is one of the most powerful ever recorded, according to the researchers. Until now, it was assumed that such violent storms occur mainly during the active phase of the sun, the solar maximum, when a particularly large number of sunspots can be observed. However, 9,200 years ago, the Sun was at a solar minimum of the approximately eleven-year solar cycle. The scientists are concerned about their findings, which they published in the journal Nature Communications, because this means that such an event can occur when it is least expected.

“These enormous storms are currently not sufficiently included in risk assessments,” says Raimund Muscheler, a geologist at Lund University, and senior author of the study. “It is of the utmost importance to analyze what these events could mean for today’s technology and how we can protect ourselves.”

Ice cores harbor countless pieces of information from times long past. Scientists can even read historical solar storms from them. Photo: Raimund Muscheler

On Earth, past solar storms can be detected in tree rings, sediment and ice cores through radionuclides – radioactive isotopes formed when charged solar particles collide with elements in Earth’s atmosphere. For the current study, the researchers used ice cores taken from various sites on the Greenland ice sheet and from one of EPICA’s drilling sites in Dronning Maud Land, Antarctica. In the ice cores, the research team, consisting of scientists from Lund University, ETH Zurich and the Alfred Wegener Institute in Bremerhaven, Germany, among others, was able to detect peak levels of the radioactive isotopes of beryllium-10 and chlorine-36.

“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,” says Raimund Muscheler.

Further analysis revealed that the storm was at least as powerful as the strongest solar storm ever discovered, dating back to 774-775 A.D., which also occurred during a solar minimum, according to the authors.

Auroras are one of the less harmful and fascinating effects of solar storms. Photo: Julia Hager

If a solar storm of this magnitude were to occur today, it could have a massive impact on our modern lives. It could cause radiation damage to satellites and power outages, and could also pose a threat to air traffic and astronauts, as well as cause communications systems to break down.

According to the authors, it is enormously important to detect more of these extreme historical solar storms in ice cores and other natural records to determine if there is a consistent pattern in the occurrence of extreme solar activity in the context of the eleven-year solar cycle. This is especially important for the planning of space missions to increase the safety of astronauts.

Julia Hager, PolarJournal

Link to the study: Chiara I. Paleari, Florian Mekhaldi, Florian Adolphi, Marcus Christl, Christof Vockenhuber, Philip Gautschi, Jürg Beer, Nicolas Brehm, Tobias Erhardt, Hans-Arno Synal, Lukas Wacker, Frank Wilhelms, Raimund Muscheler. Cosmogenic radionuclides reveal an extreme solar particle storm near a solar minimum 9125 years BP. Nature Communications, 2022; 13 (1) DOI: 10.1038/s41467-021-27891-4.

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