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

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

Geographical distribution of two haplotypes of chloroplast DNA in four oak species (Quercus) in Japan.

Chloroplast DNA polymorphism in four oak species (Quercus serrata, Q. mongolica var. crispula, Q.