The Northern Lights may have been visible across regions of the world in 2024 that are not used to seeing aurora, but despite solar activity being at a 23-year high there has been no truly extreme solar storm since 664 B.C., according to new research.
Extreme Solar Events
Six extreme solar storms have struck Earth in the past 14,500 years. They’re known as “Miyake” events after Fusa Miyake, a Japanese physicist, who in 2012 described that extreme solar events leave radioactive carbon isotopes in the growth rings of trees. However, the exact date of the most recent Miyake event has, until now, eluded scientists.
Dating extreme solar eruption events is essential for scientists who study and develop models of the sun’s activity over time.
Solar Spike
A new analysis of tree rings worldwide for carbon-14 — a naturally occurring radioactive carbon variant — has turned up a spike dating to 664 B.C. The research was published in the journal Communications Earth & Environment. Carbon-14 continually forms in Earth’s atmosphere when cosmic rays react with oxygen to form carbon dioxide. That’s absorbed by living organisms — such as trees — making carbon dating possible.
“After a few months, carbon-14 will have traveled from the stratosphere to the lower atmosphere, where it is taken up by trees and becomes part of the wood as they grow,” said co-lead researcher Irina Panyushkina of the University of Arizona Laboratory for Tree-Ring Research.
Cosmic Onslaught
Her team dissected tree rings from ancient wood samples, burned the cellulose — the main component of wood — to determine the radiocarbon content, and then compared the data to spikes in beryllium-10 found in ice cores from glaciers. Beryllium-10 also forms in the atmosphere due to an onslaught of particles from the sun.
“If ice cores from both the North Pole and the South Pole show a spike in the isotope beryllium-10 for a particular year corresponding to increased radiocarbon in tree rings, we know there was a solar storm,” said Panyushkina.
Cataclysmic Effects
Miyake events happen when the sun’s electromagnetic field weakens, allowing plasma from the sun’s surface to escape into space, ultimately leaving radiocarbon in tree rings. The now-pinpointed extreme solar event in 664 B.C. makes six Miyake events that happened in the last 14,500 years.
“If they happened today, they would have cataclysmic effects on communication technology,” said Panyushkina. “Tree rings give us an idea of the magnitude of these massive storms, but we can’t detect any type of pattern, so it is unlikely we’ll ever be able to predict when such an event is going to happen.”
Wishing you clear skies and wide eyes
