Earth

Solar superstorm in 664 BCE recorded in tree rings

Edge of the glowing, roiling surface of the sun, with bright flashes and a huge streamer of gas arcing out.
NASA’s Solar Dynamics Observatory (SDO) captured this image of a giant solar prominence on August 31, 2012. Although large and dramatic, it did not come close to having the power of a solar superstorm. Image via NASA/ SDO/ AIA/ Goddard Space Flight Center.
  • Scientists narrowed down the date of a solar superstorm that occurred more than 2,600 years ago to 664 BCE, based on a spike in carbon-14 in ancient tree rings.
  • The carbon-14 spike was found in ancient wood, including wood from an Iron Age child’s burial chamber in Russia.
  • This event was one of six solar superstorms that have occurred in the past 14,500 years, said the scientists.

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Solar superstorm date confirmed in tree rings

About 2,600 years ago, ancient Assyrians witnessed a fiery red glow across the night sky. And they recorded this significant event on a stone tablet. We now know they saw bright auroras caused by a powerful solar storm. On November 20, 2024, scientists said they believe they’ve found evidence of this event in tree rings. Furthermore, they’ve pinpointed that it happened in 664 BCE, 2,688 years ago.

The researchers published their discovery in the peer-reviewed journal Communications Earth & Environment on August 23, 2024.

If a storm of that magnitude were to occur today, it would have a serious impact on our power and communications infrastructures. But it probably would not be catastrophic. Power grids and communications systems are growing increasingly resilient in weathering solar storms. To learn more, catch up with this informative interview with David Wallace, a professor of electrical engineering at Mississippi State University.

A cross-section of a tree trunk with concentric dark circles and a metric measure superimposed.
A closeup of tree rings, with the ring corresponding to 664 BCE labeled in the image. This wood came from a larch log at an archaeological site. It was part of a child’s burial chamber. Image via Irina Panyushkina. Used with permission.

Carbon-14 in tree rings reveal an extreme solar event

Irina Panyushkina at the University of Arizona led the team studying tree rings in ancient logs. In particular, they were measuring the amount of carbon-14 in the tree rings.

They discovered a much higher concentration of carbon-14 in rings that were formed in 664 BCE. This type of carbon-14 signature, in other studies, has been associated with solar superstorms.

What is carbon-14? It’s a type of radioactive carbon that forms continually in the atmosphere. Cosmic ray particles interact with nitrogen in the upper atmosphere to create carbon-14. Eventually, carbon-14 combines with oxygen to form carbon dioxide. Over a few months, that carbon dioxide containing carbon-14 makes its way to the lower atmosphere. There, trees take it up and store it in wood tissue.

During a solar superstorm, the sun releases enormous amounts of particles. These particles strike the Earth’s atmosphere, creating a much higher amount of carbon-14 than usual. As a result, trees alive during such an event absorb and store that additional carbon-14 in that year’s tree rings.

How often do solar superstorms occur?

Scientists have identified six solar superstorms – known as Miyake events – that have happened in the past 14,500 years. They occurred in 7176 BCE, 5410 BCE, 5259 BCE, around 660 BCE, 774 CE and 993 CE.

For all Miyake events, high carbon-14 spikes were found in tree rings of ancient wood corresponding to those dates. Also, scientists have found corroborating evidence in ancient ice core samples from Greenland and Antarctica. (Higher levels of beryllium-10 and chlorine-36, found in the ice, were a result of interactions between particles from the sun during the storm and the Earth’s atmosphere.)

However, there was uncertainty about the 660 BCE event. Scientists had known, from previous tree ring data and ice core studies, that a superstorm occurred around that time, but they did not know exactly when it happened. This new study narrowed the date to 664 BCE.

When will the next solar superstorm occur? Panyushkina said:

Tree rings give us an idea of the magnitude of these massive storms, but we can’t detect any type of pattern, so it is unlikely we’ll ever be able to predict when such an event is going to happen. Still, we believe our paper will transform how we search and understand the carbon-14 spike signal of extreme solar proton events in tree rings.

The energy from this type of event not only changes the atmosphere’s radiocarbon content but also the atmosphere’s chemistry. We are trying to figure out how those short-lived and powerful events affect the Earth system as a whole.

The wood that revealed the 664 BCE solar superstorm

The researchers used dead trees that lived a long time ago to study ancient tree rings. One of the wood samples came from a well-preserved tree from a riverbank at the Polar Urals, a mountain range in Russia.

Another was an archaeological timber from an ancient larch tree. Panyushkina told EarthSky more about it:

The archaeological wood is from a small child’s [burial] chamber made of larch logs from the highlands of the Altai Mountains. It belongs to the Pazyryk culture, associated with the Siberian Scythians. I worked on an archaeological project to date these burials, known as kurgans, in 2003. Local archaeologists from Novosibirsk [in Russia] excavated the cemetery, and I collected wood samples from the kurgans for dendrochronology and dating.

A rectangular open box, made of 8 interlocked logs, reminiscent of a log cabin.
Researchers took a wood sample from this child’s burial chamber, made from larch logs. It was part of a kurgan, a type of burial mound associated with the Pazyryk culture of the Iron Age. Image via Irina Panyushkina. Used with permission.
Irregular piece of brown wood, a cross-section of a log with many narrow, dark concentric dark rings.
A cross-section of one of the logs from the burial chamber, showing the larch tree rings. Image via Irina Panyushkina. Used with permission.

Using tree rings to study past climate and to date events

Dendrochronology is the study of tree rings to date events and changes in the environment.

In temperate climates, where the seasons change, trees usually form annual rings. The size and density of each ring is determined by environmental conditions during that year. As a result, tree rings provide valuable insight into past climate in a particular region.

Tree rings can also be used for dating events. To do that, scientists build a long chronological timeline of ring patterns for a region, starting from living trees to progressively older dead trees. To date a tree ring sample, they compare the sample’s pattern to the reference chronological timeline, looking for a match. That match allows them to identify a date for their wood sample.

Bottom line: Scientists have narrowed down the date of a solar superstorm that occurred over 2,600 years ago to 664 BCE, based on a spike in carbon-14 in ancient tree rings.

Source: The timing of the ca-660 BCE Miyake solar-proton event constrained to between 664 and 663 BCE

Via University of Arizona

Read more: Biggest solar superstorm yet, glimpsed in ancient tree rings

Posted 
November 28, 2024
 in 
Earth

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