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The 774–775 Carbon-14 Spike was an increase of 1.2% in the carbon-14 content of tree rings during the years 774 or 775 AD, which was about 20 times as high as the background rate of variation. It was found during a study of Japanese cedar trees, with the year of occurrence determined through dendrochronology. 〔 A surge in a specific isotope of beryllium (10Be), detected in Antarctic ice cores, has been associated with the 774-775 event.〔 The event appears global with the same signal found in carbon-14 in tree rings from Germany, Russia, the United States and New Zealand.〔〔〔 There was also a "red crucifix" which the ''Anglo-Saxon Chronicle'' recorded in the skies of Britain for the year 774; since no supernova remnant has been found for this year this is interpretable as an aurora borealis.〔 The increase has a shape with a sharp increase of ~1.2% followed by a slow decline (see Figure 1). This shape is typical for an instant production of carbon-14 in the atmosphere,〔 indicating that the event was short in duration. The globally averaged production of carbon-14 for this event is calculated as ''Q='' (1.1-1.5)×108 atoms/cm2〔〔〔 ==Hypotheses== Several possible origins for the event have been considered. The common paradigm is that the event was caused by a solar particle event (SPE) from a solar flare that was very strong, the strongest ever known, but still within the Sun's abilities.〔〔〔〔〔 It was also proposed that the corresponding solar flare might have been triggered by a cometary impact with the Sun.〔 The solar hypothesis is supported by the fact that other similar, although weaker, events were identified, such as the event of 994 〔 which makes an exotic scenario unlikely. Plus, the comet impact scenario could have been caused by the comet X/773 B1. Another discussed scenario of the event origin is related to a gamma-ray burst.〔〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「774–775 carbon-14 spike」の詳細全文を読む スポンサード リンク
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