A series of sudden and colossal spikes in radiation levels across Earth’s history could stem from a series of unknown, unpredictable and potentially catastrophic cosmic events, a new study has revealed.
Miyake events named after the main author of the first study to describe them, spikes occur about once every 1,000 years or so and are recorded as sudden increases in radiocarbon levels in the rings of ancient trees.
The exact cause of the sudden deluges of radiation, which periodically convert an additional portion of the nitrogen in the atmosphere into carbon sucked up by the trees, remains unknown. The leading theory among scientists is that the Miyake events are solar flares which are 80 times more powerful than the strongest eruption ever recorded. But a new study, published on October 26 in the journal Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciencessuggests that the origin of radiation bursts may be even more mysterious than first thought.
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“These huge bursts of cosmic radiation, known as Miyake events, have happened about once every thousand years, but what causes them is unclear,” the lead author said. Benjamin Popeastrophysicist at the University of Queensland, Australia, said in a press release. “We need to know more because if any of them happened today it would destroy technology including satellites, internet cables, long distance power lines and transformers. global infrastructure would be unimaginable.”
Each year, temperate tree species develop a new concentric ring around their trunk which, when added together, indicates their age. Because trees suck carbon from the atmosphere, scientists can study the amount of radiation in the atmosphere during Earth’s recent history by measuring tree rings for amounts of the radioactive isotope carbon- 14 – produced when energetic cosmic rays collide with atmospheric nitrogen.
Scientists have so far spotted six Miyake events in tree rings, indicated by sudden single-year jumps in concentrations of carbon-14 and other isotopes; these occurred in the years 7176 BC, 5410 BC, 5259 BC, 660 BC, 774 AD, and 993 AD; alongside a number of other smaller events spotted at other times.
To determine if the sudden carbon-14 spikes were caused by incredibly powerful solar flares, the researchers created a simplified model of the global carbon cycle; capture tree ring data to demonstrate how carbon was produced by solar radiation and absorbed into the Earth’s atmosphere, oceans, land and organisms. By comparing their atmospheric carbon timeline with the known 11-year solar cycle, the researchers expected to find that the years of the Miyake events corresponded to times of peak solar activity.
But instead, they found that the Miyake events did not correspond to peak solar activity, and some of the events, unlike the brief flashes we recognize as solar flares, lasted one or two years.
“Rather than a single instantaneous explosion or eruption, what we may be observing is some sort of ‘storm’ or astrophysical explosion,” said first author Qingyuan Zhang, a mathematician at the University of Queensland, in the communicated.
The intensity of these unexplained cosmic barrages is hard to underestimate. The biggest solar storm ever recorded was that of 1859 Carrington Event, which, after slamming into Earth, sent powerful streams of solar particles that fried telegraph systems around the world and caused auroras to appear brighter than full moon light as far south as the Caribbean. . The storm released roughly the same energy as 10 billion 1-megaton atomic bombs. If such a powerful eruption were to hit Earth now, it would cause a ‘internet apocalypse’, blackouts and billions of dollars in damage, scientists say. But the Carrington event was 80 times less powerful than the AD 774 Miyake event.
After casting doubt on the spikes coming from conventionally understood solar flares, the researchers examined whether the Miyake events were generated by supernovae or some type of super solar flare. But these alternative theories also have holes: Supernovas sometimes produce radiocarbon spikes in Earth’s atmosphere, but sometimes they don’t; and stars like ours are not known to produce solar flares energetic enough to cause the Miyake events. Evidence for a super solar flare is also missing from ice core nitrate records recovered for the events of AD 774 and AD 993.
Venturing into the historical archives turned up only two tantalizing references. A fact in the Anglo-Saxon Chronicle (a collection of ninth-century annals recounting Anglo-Saxon history) refers to a possible dawn in the form of a “red crucifix, after sunset” spotted in the sky in 774 AD, but researchers believe it may also be an optical illusion known as the moon ring. Another account, made in 775 AD in the Chinese chronicle Jiutangshu, describes what could also have been an aurora, but its existence is so far not supported by other documents.
The researchers’ next step is to collect more data from tree rings and ice cores to better understand the timing of events and the mixtures of isotopes produced by them. But scientists’ uncertainty about the nature of events or how to predict when they will occur is “very worrying”, Pope said.
“Based on the available data, there’s about a 1% chance of seeing another in the next decade. But we don’t know how to predict that or what damage it might cause,” Pope added. “These probabilities are quite alarming and lay the groundwork for further research.”
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