@article{oai:nagoya.repo.nii.ac.jp:00011780, author = {桑名, 宏輔 and Kuwana, Kosuke and 宮原, ひろ子 and Miyahara, Hiroko and 毛受, 弘彰 and Menjo, Hiroai and 永冶, 健太朗 and Nagaya, Kentaro and 増田, 公明 and Masuda, Kimiaki and 村木, 綏 and Muraki, Yasushi and 中村, 俊夫 and Nakamura, Toshio}, journal = {名古屋大学加速器質量分析計業績報告書}, month = {Mar}, note = {Radiocarbon ^<14>C, which is one of cosmogenic radioisotopes, is a good index of solar activity. Investigation of the ^<14>C content in each tree ring gives information on the change of solar activity in the past. Variation of the ^<14>C content shows that grand solar minima, when the solar activity was extremely weak for several ten years or more, occurred many times in the past. The Maunder Minimum (1645-1720 AD), one of the grand solar minima in the last millennium, is well known to have had almost no sunspots, and then periodicity of solar activity cannot be seen. Therefore, we have investigated the periodicity of radiocarbon content in tree rings in order to clarify the characteristics of variation of solar activity during the grand solar minima. We have already obtained the ^<14>C records for 1413-1554 AD including the Spoerer Minimum and for 1617-1745 AD including the Maunder Minimum with annual time resolution by using Japanese cedar trees. As a result of frequency analysis of these radiocarbon records, we found that the Sun maintained periodic variation even if the minima. We found, however, the length of the "eleven-year" cycle during the Maunder Minimum was around 14 years and that during the Spoerer Minimum was around 11 years. This suggests that the cycle length is related to solar activity, and that the pattern of periodicity of solar activity for the type of grand solar minimum. In order to clarify these possibilities, we have investigated periodicity of solar activity in periods other than the grand solar minimum by measuring the ^<14>C content in the period between the Maunder Minimum and the Spoerer Minimum (1555-1615 AD) and 9^