Largest solar storm ever recorded found in 14 300-year-old French Alps tree rings

An international research collaboration has discovered a previously unknown massive solar storm that occurred 14 300 years ago. This finding was possible thanks to the analysis of ancient tree rings discovered in the Southern French Alps. Published today in The Royal Society’s Philosophical Transactions A: Mathematical, Physical and Engineering Sciences, the study raises questions about the Sun’s extreme behavior and the risks it poses to Earth’s technological infrastructure.

The research team, including experts from the Collège de France, CEREGE, IMBE, Aix-Marseille University, and the University of Leeds, measured radiocarbon levels in ancient trees preserved near the Drouzet River. The team found an unprecedented spike in radiocarbon levels occurring precisely 14 300 years ago, suggesting that it was caused by an extreme solar storm event.

“Radiocarbon is constantly being produced in the upper atmosphere. Extreme solar events can create short-term bursts of energetic particles, preserved as huge spikes in radiocarbon production,” said Edouard Bard, Professor of Climate and Ocean Evolution at the Collège de France and CEREGE, and lead author of the study.

According to the researchers, a similar solar storm today would have catastrophic consequences. The event could disrupt telecommunications, satellite systems, and electricity grids, resulting in economic losses amounting to billions of pounds.

Tim Heaton, Professor of Applied Statistics in the School of Mathematics at the University of Leeds, emphasized the impact on electrical infrastructure: “Extreme solar storms could permanently damage transformers in our electricity grids, causing widespread blackouts lasting months.”

The extreme solar storm discovered falls under a category of events known as Miyake Events. Nine such events have been identified in the last 15 000 years, with the most recent ones recorded in 993 AD and 774 AD. The newly-discovered event is the largest ever, roughly twice the size of the previous ones.

The true nature and frequency of Miyake Events remain poorly understood as they have not been directly observed. The study emphasizes the critical need to understand the potential risks of such solar activity to prepare and protect modern infrastructure.

“Direct instrumental measurements of solar activity are insufficient for a complete understanding of the Sun. Radiocarbon measured in tree rings provides the best way to understand the Sun’s behavior further back into the past,” said Professor Bard.

Cécile Miramont, Associate Professor of Paleoenvironments and Paleoclimates at IMBE, Aix-en-Provence University, also highlighted the importance of dendrochronology in piecing together a longer timeline to study solar activity and environmental changes.

The study serves as a wake-up call, underlining the importance of understanding solar behavior to protect global communications and energy infrastructure for the future. With much still to learn, the researchers are urging for more in-depth studies to mitigate potential risks effectively.

References:

¹ Researchers identify largest ever solar storm in tree rings   – University of Leeds – October 9, 2023

² A radiocarbon spike at 14 300 cal yr BP in subfossil trees provides the impulse response function of the global carbon cycle during the Late Glacial – Edouard Bard et al. – Philosophical Transactions of the Royal Society A: Mathematical Physical and Engineering Sciences – October 9, 2023 – https://doi.org/10.1098/rsta.2022.0206 – OPEN ACCESS

Featured image credit: The Watchers (artists representation)