太陽活動と<14>^C濃度変動

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  • Radiocarbon and the solar activity in the past

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Abstract

Production rate of radiocarbon ^<14>C in upper atmosphere depends on the solar activity through its modulation effect on the intensity of galactic cosmic ray on the earth. Tree rings record radiocarbon contents in the past because they take atmospheric carbon dioxide including radiocarbon by photosynthesis year by year. We are investigating radiocarbon contents in Yaku cedar to understand the variability of the solar activity in the last millennium and also the relation between the solar activity and the global climate change. Our recent measurement of ^<14>C contents in tree ring sampls of the Yaku cedar from the Spoerer minimum shows a large dip in the period between 1470 and 1550 AD while the data for the period between 1410 and 1470 AD are rather constant. The reason for this large varuation of ^<14>C contents is not known at present. Further measurements are necessary.

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