Thermal neutrons produced by cosmic rays interact with 14N atoms in the upper atmosphere to produce radiocarbon. This radiocarbon filters across the carbon cycle through the atmosphere, biosphere, and marine environments.
A new study by the University of Queensland demonstrated- annually resolved measurements of the radiocarbon content in tree rings have revealed rare sharp rises in carbon-14 production. These ‘Miyake events’ are likely produced by rare increases in cosmic radiation from the Sun or other energetic astrophysical sources.
The common theory until now has been that Miyake Events are giant solar flares. But, the findings challenge this.
Using advanced statistics to data from millennia-old trees, scientists determined more about radiation’ storms’.
Dr. Benjamin Pope from UQ’s School of Mathematics and Physics said, “These huge bursts of cosmic radiation, known as Miyake Events, have occurred approximately once every thousand years, but what causes them is unclear. The leading theory is that they are huge solar flares.”
“We need to know more because if one of these happened today, it would destroy technology, including satellites, internet cables, long-distance power lines, and transformers. The effect on global infrastructure would be unimaginable.”
Qingyuan Zhang, the first author, and a UQ undergraduate math student, created software to analyze all of the tree ring data that was accessible.
Mr. Zhang said, “Because you can count a tree’s rings to identify its age, you can also observe historical cosmic events going back thousands of years. When radiation strikes the atmosphere, it produces radioactive carbon-14, which filters through the air, oceans, plants, and animals, and produces an annual record of radiation in tree rings.”
“We modeled the global carbon cycle to reconstruct the process over 10,000 years to gain insight into the scale and nature of the Miyake Events.”
The results have shown that the events are not correlated with sunspot activity, and some last one or two years.
Mr. Zhang said, “Rather than a single instantaneous explosion or flare, what we may be looking at is a kind of astrophysical ‘storm’ or outburst.”
Dr. Pope said, “The fact scientists don’t know exactly what Miyake Events are or how to predict their occurrence is very disturbing. Based on available data, there’s roughly a one percent chance of seeing another one within the next decade.”
“But we don’t know how to predict it or what harms it may cause.”
“These odds are alarming and lay the foundation for further research.”
Journal Reference:
- Qingyuan Zhang, Utkarsh Sharma, et al. Modelling cosmic radiation events in the tree-ring radiocarbon record. Proceedings of the Royal Society A. DOI: 10.1098/rspa.2022.0497
