Heavy jet shower hit earth

Solar storm around 660 BC was ten times stronger than all measured today

Solar plasma outbreaks can throw millions of high-energy particles into space. A particularly severe solar storm of this kind apparently hit the earth in 660 BC. © NASA / GSFC, SDO
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Cosmic Direct Hit: In 660 BC, the Earth was hit by an extremely strong solar storm, as drill core analysis revealed. The influx of high-energy particles in this solar storm was ten times stronger than in all measured events of modern times. This suggests that the risk of such solar storms has been underestimated so far, warn the scientists.

Strong solar storms are a potential threat to satellites, communication systems and the earth's electricity grids. Because the influx of high-energy charged particles penetrates even the protective geomagnetic field and even reaches the earth's surface. In 1972, such a solar storm caused worldwide disruptions in electronics and telecommunications. In 1967, disruptions caused by a solar radiation eruption even caused almost a nuclear war.

How big is the risk?

But so far humanity has been spared from even worse solar storms. Whether this is just coincidence and how often extreme solar storms hit the earth, is so far unclear. The reason: the recording of such events with measuring instruments only goes back about 60 years. These register an abrupt increase in the influx of high-energy protons. The strongest values ​​so far were measured in a solar storm on February 23, 1956.

But for some time there has been evidence that our planet in the past has gone much fiercer Strahlenduschen. One of them occurred in 775, as evidenced by increased concentrations of the carbon isotope C-14 in annual rings of trees from this period. Another extremely strong solar storm struck the earth in 993/994, as Paschal O'Hare of the University of Lund and his colleagues report.

Abrupt isotope increase before 2, 679 years

Now O'Hare and his team have identified a third hit by such a mega solar storm. Accordingly, our planet was also in the year 660 BC exposed to a particularly strong solar radiant shower. Evidence for this was provided by abrupt increases in the carbon-14 content in tree rings, but also by increased levels of the isotopes beryllium-10 and chlorine-36 in an ice core of the North Greenland Ice Core Project (NGRIP). display

An abrupt increase in beryllium 10 and chlorine 26 levels indicates a strong shower of sunlight from a solar storm. O'Hare et al. / PNAS

"The beryllium-10 peak resembles in its form strongly those of the two extreme solar storms in the years 775 and 994", the researchers report. In addition, at that time all three isotopes at the same time had skyrocketed. These results argue that at that time a strong stream of particles hit the earth. The most likely cause for this is a solar storm, the scientists say. Because a gamma-ray burst would have produced other isotope ratios.

An order of magnitude stronger

It seems clear that in the year 660 BC an extremely strong solar storm hit Earth. O'Hare and his team estimate that about 20 billion high-energy protons per square centimeter were injected into the earth. "Thus, this event was a magnitude greater than the largest instrumental measured solar storm of 23 February 1956, " say the researchers. Thus, there are already three historical solar storms known, which exceed the values ​​measured today with far more intensity.

"If this solar storm had occurred today, it would have had a severe impact on our high-tech society, " says O'Hare's colleague Raimund Muscheler. "That's why we need to protect ourselves better against solar storms in the future - the risk has so far been underestimated." (Proceedings of the National Academy of Sciences, 2019; doi: 10.1073 /pnas.1815725116)

Source: Lund University

- Nadja Podbregar