Abstract
Cosmic rays interact with the Earth’s atmosphere to produce 14C, which can be absorbed by trees. Therefore, rapid increases of 14C in tree rings can be used to probe previous cosmic-ray events. By this method, three 14C rapidly increasing events have been found. Plausible causes of these events include large solar proton events, supernovae, or short gamma-ray bursts. However, due to the lack of measurements of 14C by year, the occurrence frequency of such 14C rapidly increasing events is poorly known. In addition, rapid increases may be hidden in the IntCal13 data with five-year resolution. Here we report the result of 14C measurements using an ancient buried tree during the period between bc 3388 and 3358. We found a rapid increase of about 9‰ in the 14C content from bc 3372 to bc 3371. We suggest that this event could originate from a large solar proton event.
Highlights
Cosmic rays interact with the Earth’s atmosphere to produce 14C, which can be absorbed by trees
A large amount of cosmic rays can be generated on a short time scale by high-energy phenomena, such as supernovae (SNe)[5] and large solar proton events (SPEs)[6,7,8]
Because the intensity of this event is less than that of AD 774–775 event, the energy of a typical short gamma-ray bursts (GRBs) located at a few kpc can provide necessary energy[14] for this event
Summary
Cosmic rays interact with the Earth’s atmosphere to produce 14C, which can be absorbed by trees. Rapid increases of 14C in tree rings can be used to probe previous cosmic-ray events. By this method, three 14C rapidly increasing events have been found. A large amount of cosmic rays can be generated on a short time scale by high-energy phenomena, such as supernovae (SNe)[5] and large solar proton events (SPEs)[6,7,8]. Rapid increases of 14C content in tree rings are valuable tools to explore high-energy phenomena occurred in ancient times. We report the measurement of 14C content for an ancient buried tree in China during the period BC 3388–3358 to search 14C increase events, and find a rapid increase from BC 3372 to BC 3371. Considering the occurrence rate of the rapid 14C increase events, the 14C event could originate from a large SPE
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