American and European scientists who studied the concentration of the carbon-14 isotope in the annual tree rings of Switzerland, Germany, Ireland, Russia and the United States, were able to identify two previously unknown superflares on the Sun, which occurred in 7176 and 5259 BC. An article about this is pending in the journal Nature Communications, a preprint of the article is available on the In Review website.
The increase in atmospheric 14C by about 2% recorded for these events exceeds all previously known 14C peaks, but after taking into account the variations in the geomagnetic field, they are still comparable with the largest event of this kind, already detected earlier. It happened in 775 AD. Ice cores allow similar, albeit somewhat less accurate, measurements of beryllium-10 and chlorine-36 concentrations. Taken together, all of these methods can provide a very accurate description of such prehistoric events. These cataclysms are precisely time-stamped to correlate tree ring data with ice cores, providing information on extreme solar events.
In those days on Earth, nomadic hunter-gatherer tribes gradually gave way to the first agricultural settlements, and the lack of any modern technology allowed both of them to endure solar flares without any problems, except perhaps observing unusual flashes of the northern lights far to the south. However, mankind is well aware of the so-called Carrington event of 1859, when solar flares caused significant damage to Earth's technologies, causing a powerful geomagnetic storm, which manifested itself not only in unusual auroras, but also in electrical short circuits and sparks in telegraph lines. The three events under consideration were more powerful than this cataclysm by another order or two. If such an event occurs today, it could have the most devastating consequences for satellites in orbit and ground infrastructure. In March 1989, due to a geomagnetic storm in Canadian Quebec, electricity was cut for 12 hours, then the power system of the entire province was damaged, and this event was much weaker than even in 1859.