Evidence of the biggest ever solar storm 14,300 years ago has been found in ancient tree rings.
Such a massive storm today on the scale of the newly discovered one would be ‘catastrophic’ for modern technology, say scientists.
It would potentially wipe out telecommunications and satellite systems, cause massive electricity grid blackouts, and cost the global economy billions of pounds.
The research team say it is vitally important to understand the Sun’s extreme behaviour and the risks it poses to Earth.
A huge spike in radiocarbon levels was identified by an international team of scientists who analysed ancient tree-rings found in the French Alps.
‘Extreme solar storms could have huge impacts on Earth,’ said Professor Tim Heaton, of the University of Leeds. ‘Such super storms could permanently damage the transformers in our electricity grids, resulting in huge and widespread blackouts lasting months.
‘They could also result in permanent damage to the satellites that we all rely on for navigation and telecommunication, leaving them unusable.
‘They would also create severe radiation risks to astronauts.’
Nine such extreme solar storms – known as Miyake Events – have now been identified as having occurred over the last 15,000 years.
The most recent confirmed Miyake Events occurred in 993 CE and 774 CE.
The newly-identified 14,300-year-old storm is, however, the largest that has ever been found – roughly twice the size of the two in the Middle Ages.
What is a solar storm?
Solar storms occur when magnetic eruptions on the Sun’s surface – solar flares or coronal mass ejections – hit Earth’s atmosphere.
Within this energy blast are high-energy protons – one of the three main particles that make up an atom, alongside neutrons and electrons.
When the protons collide with atoms and molecules in the upper atmosphere they create a layer of loose, or free, electrons, which gather at the bottom of the ionosphere and interfere with radio waves.
In addition to hampering communications, large solar energy blats pose a radiation threat to humans in space – and even passengers in aircraft at high altitudes in more extreme cases.
Scientists say the exact nature of those storms remains very poorly understood as they have never been directly observed instrumentally.
‘We do not know what causes such extreme solar storms to occur, how frequently they might occur, or if we can somehow predict them,’ said Professor Tim Heaton.
The research team measured radiocarbon levels in ancient trees preserved within the eroded banks of the Drouzet River, near Gap, in the Southern French Alps.
Lead author Professor Edouard Bard, of the Collège de France, said: ‘Radiocarbon is constantly being produced in the upper atmosphere through a chain of reactions initiated by cosmic rays.
‘Recently, scientists have found that extreme solar events, including solar flares and coronal mass ejections, can also create short-term bursts of energetic particles which are preserved as huge spikes in radiocarbon production occurring over the course of just a single year.’
The tree trunks, which are subfossils – remains in which the fossilisation process is not complete – were sliced into tiny single tree-rings.
Analysis of the individual rings identified the ‘unprecedented’ spike in radiocarbon levels occurring precisely 14,300 years ago.
By comparing the spike with measurements of beryllium, a chemical element found in Greenland ice cores, the team suggest that the spike was caused by a massive solar storm that would have ejected ‘huge’ volumes of energetic particles into Earth’s atmosphere.
‘Direct instrumental measurements of solar activity only began in the 17th Century with the counting of sunspots,’ said Professor Bard.
‘Nowadays, we also obtain detailed records using ground-based observatories, space probes, and satellites. However, all these short-term instrumental records are insufficient for a complete understanding of the Sun.
‘Radiocarbon measured in tree-rings, used alongside beryllium in polar ice cores, provide the best way to understand the Sun’s behaviour further back into the past.’
‘Finding such a collection of preserved trees was truly exceptional,’ said Professor Cécile Miramont,,of Aix-en-Provence University in France.
‘By comparing the widths of the individual tree rings in the multiple tree trunks, we then carefully pieced together the separate trees to create a longer timeline using a method called dendrochronology.
‘This allowed us to discover invaluable information on past environmental changes and measure radiocarbon over an uncharted period of solar activity.’
The largest directly-observed solar storm occurred in 1859, and is known as the Carrington Event.
It caused massive disruption on Earth – destroying telegraph machines and creating a night-time aurora so bright that birds began to sing, believing the Sun had begun to rise.
The Sun is currently nearing the peak of its 11-year solar cycle, resulting in a number of powerful solar storms have been fired towards Earth – including a number that caused radio blackouts.
The findings were published in The Royal Society’s Philosophical Transactions A: Mathematical, Physical and Engineering.
MORE : What is going on with the Sun right now?
MORE : Earth hit by massive solar flare knocking out radio across US – and it won’t be the last
