In September 1859, the same year Darwin published On the Origin of Species, telegraph systems in Europe and North America stopped working and began emitting sparks, in some cases causing fires. Just hours earlier, researchers had observed the first confirmed solar flare—an intense burst of radiation from the Sun—a warning that something big was about to hit our planet.
Much of the northern and southern skies were illuminated with bright auroras (the aurora borealis and aurorae), indicating that a powerful solar storm was approaching. This storm, later called the Carrington event, was one of the most powerful on record. However, a recent paper Nature We have shown that in the not-so-distant past, Earth suffered from much more extreme solar storms.
Evidence for these storms comes primarily from analysis of levels of radioactive carbon, known as radiocarbon or carbon-14, in tree rings. Solar storms cause disturbances in the Earth’s magnetic shield, or magnetosphere. One common way they occur is through coronal mass ejections (emissions of charged particles from the Sun) that reach the Earth and penetrate the magnetosphere.
Extreme solar storms can spell disaster for our high-tech society, as they can damage satellites and knock out communications and global power grids. The strength of some past extreme solar storms, as revealed in tree rings, suggests that they wreaked havoc on our technological infrastructure on an unprecedented scale. For example, an extreme solar storm known to have occurred in 774 AD eclipsed the Carrington event.
Radiocarbon measurements
Radiocarbon, or carbon dating, has been widely used for decades to date once-living objects like bone, wood, and leather. When plants and animals die, the radiocarbon in them decays at a predictable rate. So scientists can estimate how long ago an organism died by measuring how much radioactive carbon remains in an object like bone.
But over the past decade, scientists have discovered that extreme solar storms can affect the amount of radioactive carbon absorbed by living organisms like trees. This gives researchers the ability to search for extreme solar events that aren’t recorded in history books and date them precisely.
The amount of radiocarbon in the atmosphere changes over time, so radiocarbon dating can give misleading ages. For this reason, significant efforts have been made over the years to “calibrate” radiocarbon records to make them more accurate. This means correlating them with other materials of known age.
These could be trees, which can be dated by growth rings, or stalagmites and corals, which can be dated by other methods. When combined with the science of tree-ring dating (dendrochronology), the radiocarbon signal from a severe solar storm can provide a reference point for a full year. This can help make radiocarbon dating even more accurate.
By looking at the available evidence for these extreme solar storms, we can now begin to understand how often they occur. The evidence tells us a lot about the global carbon cycle, ocean and atmospheric circulation (how heat is redistributed across the Earth’s surface), and how the Sun works.
Solar storms alter radioactive carbon in trees
In 2012, a group led by Fusa Miyake of Nagoya University in Japan found that extreme solar storms can cause dramatic changes in the concentration of radioactive carbon in tree rings. Before this, it was believed that the rate of radioactive carbon production did not change significantly over short periods of time, so annual measurements of radioactive carbon in the past were unlikely to be of particular interest.
They found a large increase in atmospheric radiocarbon production associated with the AD774 extreme storm. Other extreme events were confirmed to have occurred in AD993, 660 BC, 5259 BC, and 7176 BC.
The most intense solar storm we have detected in the radiocarbon record occurred about 14,370 years ago, at the end of the last ice age.
We don’t yet know whether these events are larger versions of normal solar storms, called Black Swan events, or whether they are caused by different physical phenomena. As more intense solar storms are detected from the radiocarbon record, they will add to our understanding of the physical processes occurring on our parent star.
One of the biggest threats of a major solar storm is the potential to instantly destroy the entire satellite fleet (except for low-altitude satellites that are permanently protected by the geomagnetic field) and knock out power grids. It is important to be able to predict these events and warn grid operators in advance.
Radiocarbon records may reveal more extremes in coming years
The scientific community is rushing to analyze old trees from different parts of the world in an effort to strengthen existing evidence and identify new extreme solar storms from the past.
Improving our understanding of these extraordinary events is important not only for accurate radiocarbon dating, but also for understanding the processes occurring on the Sun and our planet. It could also help us prepare for the next extreme solar storm. We can’t yet predict when that will happen, but a new understanding of the past tells us it will happen sooner rather than later.
Source: Port Altele
