The enigmatic chemical trace of unidentified origins that has been concealed for ages inside the trunks of the trees of Earth's forests has just become more perplexing.
In the last 10 years, researchers have found evidence on Earth of six severe bursts of radiation that occurred at various times and locations throughout the past 9,300 years and are referred to as Miyake events. The most widely accepted theory is that these mystery signs were left behind by gigantic solar storms. This theory has led some experts to warn that the next Miyake event might bring the electrical system of the whole planet to its knees. However, recent study that was just published in the October issue of the Proceedings of the Royal Society A reveals that solar flares are not the only possible explanation for the mysterious radiation.
According to physicist Gianluca Quarta of the University of Salento in Lecce, Italy, who was not involved in the research, the discovery highlights the need for more studies into these unusual bursts, which have the potential to do damage to our civilization in the future. "What we now know does not seem to make sense," or "Something doesn't add up."
The Miyake occurrences were first found to have occurred in trees. Trees' trunks build up layers, often known as rings, as they mature, and these rings are able to preserve chemical imprints from their environment. Researchers are able to get hints about climatic conditions that occurred hundreds of years, even thousands of years ago by examining the chemical makeup of individual tree rings (SN: 6/1/20).
A physicist named Fusa Miyake from Nagoya University in Japan was researching the tree rings of Japanese cedar trees in 2012 when she discovered a sharp spike in radiocarbon in rings that dated back to approximately the year 774 A.D. Radiocarbon is a variant of carbon that can form when cosmic radiation strikes the atmosphere of Earth. Since that time, five other bursts of the same kind, which are now known as Miyake events, have been discovered in the tree rings of various locations throughout the globe as well as in the ice cores of the polar regions.
A significant number of experts believe that the spikes originated from somewhere other than Earth because of their widespread distribution. The most widely accepted hypothesis is that very powerful solar flares or storms are responsible for bombarding Earth with intense bursts of radiation (SN: 2/26/21).
The Carrington event, which occurred in 1859, was the most violent solar storm ever recorded in human history. It caused telegraph cables to break and ignited a circuit fire in Pittsburgh. Benjamin Pope, a physicist at the University of Queensland in St. Lucia, Australia, claims that the radiation levels linked with Miyake occurrences are more than 80 times higher than those associated with the Carrington incident. They can provide significant challenges to the development of technology all around the world.
However, there are flaws in the theory of the solar storm. According to the findings of some academics, the radiation levels produced by the 774 event would have been far too enormous to have been caused by a single solar flare. Ice cores, which can also store chemical traces of solar flares, have not yet shown evidence of higher solar activity for every Miyake event. This is despite the fact that ice cores can preserve chemical traces of solar flares.
As a result, Pope and his fellow researchers decided to investigate the leading theory. Using computer models of the Earth's carbon cycle, they examined all of the tree ring data that was made available to the public on the six Miyake incidents. The team was able to use this information to compute the length of time, the timing, and the magnitude of each event.
If the Miyake episodes are related to solar activity, then they could coincide with solar maximum, which take place once every 11 years on average and are characterised by an increase in the frequency of solar flares. However, the researchers were unable to find any connection between the occurrences associated with Miyake and any part of the solar cycle. In addition, the researchers discovered that two of the occurrences seemed to linger for more than a year, which is an abnormally lengthy duration for solar storms, which generally run for hours or days.
If solar flares were really the origin of the occurrences, then trees located closer to the poles, where the protective magnetic field of the Earth is thinner, should contain greater amounts of radiation from the Miyake event. However, the researchers did not discover any such pattern.
According to Pope, the data don't completely disprove the solar flare idea. According to him, a lack of adequate data on tree rings may be concealing a connection between solar activity and Miyake episodes. Researchers at the Australian Nuclear Science and Technology Organization are now analysing new data from ice cores in Antarctica, and they plan to publish their findings in the next year. These findings may give further answers.
Quarta acknowledges that solar flares are still a potential explanation for the incidents. The results might be influenced by nuances in the carbon cycle of the Earth that were not captured by the models. It's possible, for instance, that various types of trees or different latitudes cause them to metabolise radiocarbon at different rates.
Even though the riddle has not been solved, Pope is not losing any sleep about the possibility of another Miyake incident taking place in the near future. According to him, the likelihood of one occurring in the subsequent ten years is around one percent. If I had to walk to work, I'd be more concerned about being struck by a bus than anything else.
CITATIONS
Q. Zhang et al. Modelling cosmic radiation events in the tree-ring radiocarbon record. Proceedings of the Royal Society A. Vol. 478, October 2022. doi: 10.1098/rspa.2022.0497.
F. Miyake et al. A single-year cosmic ray event at 5410 BCE registered in 14C of tree rings. Geophysical Research Letters. Vol. 48, June 16, 2021. doi: 10.1029/2021GL093419.
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