– Scientists have identified a new type of solar event that occurred 7,000 years ago. In the year 5480 B.C. abnormal solar activity affected life on Earth. What was the cause?
By measuring carbon-14 levels in tree rings, which reflect the effects of cosmic radiation on the atmosphere at the time, an international team of scientists led by researchers at Nagoya University, along with US and Swiss colleagues discovered a change in 14C that was more abrupt than any found previously, except for cosmic ray events in AD 775 and AD 994.
When the activity of the sun changes, it has direct effects on our planet. For example, when the sun is relatively inactive, the amount of a type of carbon called carbon-14 increases in the earth’s atmosphere.
Because carbon in the air is absorbed by trees, carbon-14 levels in tree rings actually reflect solar activity and unusual solar events in the past. The team took advantage of such a phenomenon by analyzing a specimen from a bristlecone pine tree, a species that can live for thousands of years, to look back deep into the history of the Sun.
The team attempted to develop an explanation for the anomalous solar activity data by comparing the features of the 14C change with those of other solar events known to have occurred over the last couple of millennia.
“Although this newly discovered event is more dramatic than others found to date, comparisons of the 14C data among them can help us to work out what happened to the sun at this time,” Fusa Miyake of Nagoya University says.
She adds, “We think that a change in the magnetic activity of the sun along with a series of strong solar bursts, or a very weak sun, may have caused the unusual tree ring data.”
The poor understanding of the mechanisms behind unusual solar activity has hampered efforts to definitively explain the team’s findings, but researchers hope that additional studies, such as telescopic findings of flares given off by other sun-like stars, could lead to an accurate explanation.
This event could be similar to when our planet was hit by an extremely intense burst of high-energy radiation of unknown origin sometime between AD 774 and AD 775. Whether that energy burst was a result of result of extraordinary auroras or gigantic solar flares has puzzled scientists for some years.