Prolonged production of 14C during the ~660 BCE solar proton event from Japanese tree rings

Abstract Annual rings record the intensity of cosmic rays (CRs) that had entered into the Earth’s atmosphere. Several rapid 14 C increases in the past, such as the 775 CE and 994CE 14 C spikes, have been reported to originate from extreme solar proton events (SPEs). Another rapid 14 C increase, also... View More