New evidence in Greenland's ice cores show that an extreme solar storm known as a solar proton event (SPE) hit the earth 2,679 years ago. The research published Monday in the journal Proceedings of the National Academy of Sciences documented the third known occurrence of an SPE, the other two occuring 1,245 and 1,025 years ago.
The stellar events happen after a massive solar flare or coronal mass ejection on the sun, sending streams of particles towards the Earth's atmosphere. This triggers a higher rate of radionuclide production including carbon-14, beryllium-10, and chlorine-36 (radionuclides are unstable atoms with excess nuclear energy).
SPEs can cause excessive amounts of ultraviolet radiation to reach the Earth's surface, and while not extremely detrimental to affected life forms, experts are more concerned about their potential to destroy our technological infrastructure. They pose “a threat to modern society in terms of communication and navigation systems, space technologies, and commercial aircraft operations,” the authors wrote in the paper.
With this recent discovery, we now know that the stellar event happens more often than we think—about once every 1,000 years. “I think the statistical bases for occurrence rate estimates is very weak,” one of the authors, Raimund Muscheler, said. “We now have three of such events—660 BCE, 775 AD and a slightly weaker one at 993 AD—but to say that these occur on average every 1,000 years would be very speculative. We will need more high-resolution carbon-14, beryllium-10, and chlorine-36 data to get this occurrence rate more robustly.”
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