Super-powerful solar storms hit Earth in the past — and could recur in the future

Solar storms can be much more powerful — as much as ten times more powerful — than we previously thought, according to a new study led by researchers from Lund University.  They found evidence of a massive solar storm in 660 BCE in chemical traces formed in the atmosphere which then rained down and were found in ice cores from Greenland.

"We saw a huge spike in the ice cores," said Florian Mekhaldi, a co-author of the paper that announced this discovery, and a postdoctoral researcher in the Department of Geology at Lund University in Sweden.

"That's a signal that Earth was hit by some huge event."

• Research in the journal Proceedings of the National Academy of Sciences

Previous research by the group had found evidence of two other major solar storms in ice cores that date back to 775 and 994 CE.

Taken together, they prove that massive solar storms have happened throughout history that were much more powerful than anything we've been able to detect in the past 70 years, when we first began to monitor solar activity in earnest.

This suggests that we might be underestimating the risk of solar storms if our assessment was based on our relatively recent monitoring efforts, said Mekhaldi.

What are solar storms?

Solar storms are violent bursts of charged particles that are driven off the sun by the sun's magnetic field.

A particularly powerful storm on the surface of the star can end up forming solar flares and coronal mass ejections that send particles at tremendous speed towards us.

They don't have much impact on biological life on Earth.  But their interaction with the Earth's magnetic field can cause severe disruptions to our electric grid and satellite system by causing electric currents to surge. 

For the past 70 years, scientists have been using satellites to monitor solar storms, and occasionally we've experienced large ones that have caused significant disruption. A large solar storm caused a massive power outage in Quebec in 1989 and another had similar impacts in Malmö, Sweden in 2003.

But according to Mekhaldi, they were rather mild events that aren't even detectable in the ice cores he examined.

The proof is in the ice

The research team found large concentrations of radioactive isotopes beryllium-10 and chlorine-36 left over from the 660 BCE solar storm when they looked at ice cores from Greenland.

"These cosmic rays are so high energy, they produce a lot of particles in the atmosphere," said Raimund Muscheler, the senior author of the paper and a professor in the department of geology at Lund University.

"The more they come into the atmosphere, they more they produce in the ice cores and you can see back in time this way."

If such a powerful solar storm were to occur today in our modern technological society, it could take weeks to months to restore power, and cost trillions of dollars in damages and repairs, according to Mekhadi.

Given the enormous repercussions, we need to better understand its impact on Earth and take precautions.

For now, scientists can't say how often these massive solar storms occur, or when the next one will happen. But Mekhaldi and his colleagues will continue to search for traces of other major solar storms in the ice to get a better picture of how often they occur.