14,300-yr-old tree rings reveal largest-ever solar storm

London : An international team of scientists has discovered a huge spike in radiocarbon levels 14,300 years ago by analysing ancient tree-rings found in the French Alps. The radiocarbon spike was caused by a massive solar storm, the biggest ever identified.

The largest, directly-observed, solar storm occurred in 1859 and is known as the Carrington Event. It caused massive disruption on Earth -- destroying telegraph machines and creating a night-time aurora so bright that birds began to sing, believing the sun had begun to rise.

Nine such extreme solar storms -- known as Miyake Events -- have now been identified as having occurred over the last 15,000 years. The most recent confirmed Miyake Events occurred in 993 AD and 774 AD.

This newly-identified 14,300-year-old storm is, however, the largest that has ever been found -- roughly twice the size of these two. However, the Miyake Events (including the newly discovered 14,300-yr-old storm) would have been a staggering entire order-of-magnitude greater in size.

In the study, researchers from the UK, France and Czech Republic measured radiocarbon levels in ancient trees preserved within the eroded banks of the Drouzet River, near Gap, in the Southern French Alps.

The tree trunks, which are subfossils -- remains whose fossilisation process is not complete -- were sliced into tiny single tree-rings. Analysis of these individual rings identified an unprecedented spike in radiocarbon levels occurring precisely 14,300 years ago.

By comparing this radiocarbon spike with measurements of beryllium, a chemical element found in Greenland ice cores, the team in the paper published in Philosophical Transactions of the Royal Society A: Mathematical Physical and Engineering Sciences, proposed that the spike was caused by a massive solar storm that would have ejected huge volumes of energetic particles into Earth's atmosphere.

The researchers said that the occurrence of similar massive solar storms today could be catastrophic for modern technological society, potentially wiping out telecommunications, satellite systems and electricity grids -- and costing us billions of pounds.

They warn that it is critical to understand the future risks of events like this, to enable us to prepare, build resilience into our communications and energy systems and shield them from potential damage.

"Extreme solar storms could have huge impacts on Earth. Such super storms could permanently damage the transformers in our electricity grids, resulting in huge and widespread blackouts lasting months. They could also result in permanent damage to the satellites that we all rely on for navigation and telecommunication, leaving them unusable. They would also create severe radiation risks to astronauts," said Tim Heaton, Professor of Applied Statistics in the School of Mathematics at the University of Leeds in the UK.