Miyake event

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.

A 2023 study dated the largest known Miyake event between 12,350 and 12,349 BCE, identified by an international team 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, this event has not yet been independently confirmed in wood from other regions, nor is it 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.

Discovery

The events are named after the Japanese physicist Fusa Miyake who, as a doctoral student, was the first to identify these radiocarbon spikes and published the results with co-authors in 2012 in the journal Nature. The investigation at that time found a strong ¹⁴
C increase in the annual rings of Japanese cedars for the years 774/775. The event of 775 was independently discovered, using the low-resolution IntCal data.

In 2013, Miyake and co-authors published the discovery of another similar radiocarbon spike in the years 993/994. In December 2013, Miyake received her Doctor of Science degree from Nagoya University.