A massive solar storm hit Earth 2,700 years ago. This solar storm known as solar proton event (SPE) is about 10 times stronger than any recorded in modern history.

Solar Proton Event

SPEs occur in the wake of a massive solar flare or coronal mass ejection. These events send streams of particles, which include high-energy protons, toward Earth where these interact with the planet's atmosphere. This sets off reactions that raise the production rate of radionuclides — unstable atoms with excess nuclear energy, which include carbon-14, beryllium-10, and chlorine-36.

Should a similar event happen today, it could potentially destroy modern technological infrastructure such as those crucial to navigation and communication.

Evidence Found On Ice Cores From Greenland

Spikes of carbon 14 in tree rings are associated with SPEs, but the occurrence of these events can also be detected as elevated levels of beryllium-10 and chlorine-36 in ancient ice cores.

In a new study, Raimund Muscheler from Sweden's Lund University and colleagues found evidence of a huge solar storm that occurred around 660 BC using two ice cores from Greenland. The ice samples have elevated levels of beryllium-10 and chlorine-36 isotopes.

"This study provides evidence of an enormous solar storm around 2,610 B.P. It is only the third such event reliably documented and is comparable with the strongest event detected at AD 774/775," Muscheler and colleagues wrote in their study published in the journal PNAS.

The findings back up results of an earlier work. In 2017, scientists identified a spike of carbon-14 in tree rings around the same time the SPE occurred.

Damaging Event

If an SPE occurs again today, the researchers warned it could have devastating impact. These events can temporarily degrade the Earth's ozone layer, which would allow excessive amount of harmful ultraviolet radiation to reach the ground. This may not trigger a mass extinction, but it could pose a problem for a society that has become dependent on electricity and other technologies.

"Today, we have a lot of infrastructure that could be badly damaged, and we travel in air and space where we are much more exposed to high-energy radiation."Muscheler said