Massive Solar Storm 2,687 Years Ago Recorded in Tree Rings

A massive solar storm struck Earth nearly 2,700 years ago, with evidence preserved in tree rings. This event, unlike modern solar storms, was so rare that only six similar incidents have been recorded in the past 14,500 years, with the most recent occurrence taking place between 664 and 663 BCE.

These extraordinary solar storms are known as Miyake Events, named after Japanese physicist Fusa Miyake, who first identified them in 2012. Miyake’s research highlighted sharp increases in carbon-14, a radioactive isotope found in tree rings, which marked the signature of these rare solar storms.

A team from the University of Arizona, led by Irina Panyushkina and Timothy Jull, has been studying tree rings to uncover evidence of these ancient solar storms. Their findings are published in Communications Earth & Environment. The researchers focused on how cosmic radiation, when interacting with nitrogen, forms carbon-14 in the atmosphere. This carbon-14 then travels through the atmosphere, enters trees via photosynthesis, and becomes embedded in the wood, leaving a record in the tree rings.

Panyushkina warned that if a Miyake Event occurred today, it would have catastrophic consequences, particularly for communication technology, as the solar storms could disrupt satellites and power grids.

To study these ancient events, the team collected wood samples from trees that had been preserved in riverbanks or found during archaeological excavations. By analyzing the radiocarbon content in the tree rings, they could pinpoint when these solar storms occurred.

They also compared the tree-ring data with ice cores, which serve as natural archives of past climate events. Beryllium-10, another isotope created when solar particles interact with the atmosphere, also shows up in ice cores, offering additional evidence of solar storms.

By matching the spikes of carbon-14 in tree rings with beryllium-10 spikes in ice cores from both the North and South Poles, the researchers could confirm the occurrence of a solar storm in a specific year. This cross-referencing helps provide a more complete picture of the solar storms that have impacted Earth in the past.