Английская Википедия:774–775 carbon-14 spike
Шаблон:Short description The 774–775 carbon-14 spike is an observed increase of around 1.2% in the concentration of the radioactive carbon-14 isotope in tree rings dated to 774 or 775 CE, which is about 20 times higher than the normal year-to-year variation of radiocarbon in the atmosphere. It was discovered during a study of Japanese cedar tree-rings, with the year of occurrence determined through dendrochronology.[1] A surge in beryllium isotope Шаблон:Chem, detected in Antarctic ice cores, has also been associated with the 774–775 event.[2] The 774–775 CE carbon-14 spike is one of the several Miyake events and it produced the largest and most rapid rise in carbon-14 ever recorded.[3][4]
The event appears to have been global, with the same carbon-14 signal found in tree rings from Germany, Russia, the United States, Finland, and New Zealand.[2][5][6]
The signal exhibits a sharp increase of around 1.2% followed by a slow decline, which is consistent with an instant production of carbon-14 in the atmosphere,[2] indicating that the event was short in duration. The globally averaged production of carbon-14 for this event is Шаблон:Nowrap.[2][7][8]
Hypotheses
Several possible causes of the event have been considered.
Шаблон:Blockquote The "red crucifix" recorded by the Anglo-Saxon Chronicle has been variously hypothesised to have been a supernova[9] or the aurora borealis.[2][10]
In China, there is only one clear reference to an aurora in the mid-770s, on 12 January 776.[11][12] However, an anomalous "thunderstorm" was recorded for 775.[13]
The most widely accepted theory is that the event was caused by a solar particle event (SPE) from a very strong solar flare, perhaps the strongest known.[2][7][14][15][16][3] Another proposed origin, involving a gamma-ray burst,[8][17] is regarded as unlikely, because the event was also observed in isotopes Шаблон:Chem and Шаблон:Chem.[16]Шаблон:Clarify
Frequency of similar events
The event of 774 is the strongest spike over the last 11,000 years in the record of cosmogenic isotopes,[14] but several other events of the same kind (Miyake events) have occurred during the Holocene epoch.[14] The 993–994 carbon-14 spike was about 60% as strong;[18] another event occurred in Шаблон:Circa.[19][20] In 2023 the strongest yet discovered event was reported, which occurred in 12,350-12,349 BC.[21]
The event of 774 did not have any significant consequences for life on Earth,[22][15] but had it happened in modern times, it might have produced catastrophic damage to modern technology, particularly to communication and space-borne navigation systems. In addition, a solar flare capable of producing the observed isotopic effect would pose considerable risk to astronauts.[23]
Шаблон:Chem variations are poorly understood, because annual-resolution measurements are available for only a few periods (such as 774–775).[24] In a 2017 study, a Шаблон:Chem increase of (2.0%) was associated with a 5480 BCE event, but it is not associated with a solar event because of its long duration, but rather to an unusually fast grand minimum of solar activity.[24]
See also
- Bomb pulse, a man-made C-14 spike
- Carrington Event
- List of solar storms
References
External links
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