Miyake event

A Miyake event is an observed sharp enhancement of the production of cosmogenic isotopes by cosmic rays. It can be marked by a spike in the concentration of radioactive carbon isotope ¹⁴
C in tree rings, as well as ¹⁰
Be and ³⁶
Cl in ice cores, which are all independently dated. At present, five significant events are known (7176 BCE, 5259 BCE, 664-663 BCE (historically referred to as 660 BCE), 774 CE, 993 CE) for which the spike in ¹⁴
C is quite remarkable, i.e. above 1% rise over a period of two years, and four more events (12,350 BCE, 5410 BCE, 1052 CE, 1279 CE) need independent confirmation. It is not known how often Miyake events occur, but from the available data it is estimated to be every 400 to 2,400 years.

There is strong evidence that Miyake events are caused by extreme solar particle events and they are likely related to super-flares discovered on solar-like stars. Although Miyake events are based on extreme year-to-year rises of ¹⁴
C concentration, the duration of the periods over which the ¹⁴
C levels increase or stay at high levels is longer than one year. However, a universal cause and origin of all the events is not yet established, and some of the events may be caused by other phenomena coming from beyond the Solar System, such as a gamma-ray burst.

In 2023, the largest known Miyake event was reported between 12,350 and 12,349 BCE. It was identified by a study conducted by an international team of researchers who measured radiocarbon levels in ancient trees recovered from the eroded banks of the Drouzet River, near Gap in the Southern French Alps. Although the ¹⁴
C increase was nearly double that for the next strongest spike in 774 CE, the strength of the corresponding solar event was only 18 % higher, because of the combined effect of the lower atmospheric CO2 level and weaker geomagnetic field However, the event has not yet been independently confirmed in wood from other regions, nor it is reliably supported by a clear corresponding spike in other isotopes, such as beryllium-10, that are needed to reconstruct the spectrum of solar energetic particles.

A Miyake event occurring in modern conditions might have significant impacts on global technological infrastructure such as satellites, telecommunications, and power grids.