2004 Fiscal Year Final Research Report Summary
A study of the solar activity variability in the past millennium by precise radiocarbon measurement
| Project/Area Number |
14340071
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
素粒子・核・宇宙線
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| Research Institution | Nagoya University |
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Principal Investigator |
MASUDA Kimiaki Nagoya University, Solar-Terrestrial Environment Laboratory, Associate Professor, 太陽地球環境研究所, 助教授 (40173744)
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| Project Period (FY) |
2002 – 2004
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| Keywords | Radiocarbon / Solar activity / Accelerator Mass spectrometry / Cosmic rays / The Maunder Minimum / The Spoerer Minimum / Little Ice Age / Climate change |
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| Research Abstract |
This project aimed to investigate variability of solar activity and structure of interplanetary magnetic field in the last millennium by radiocarbon in tree rings during grand minima of solar activity with accelerator mass spectrometry. For this purpose we prepared samples and measured radiocarbon content with great care on high precision and tried to find small change of radiocarbon content in the Spoerer and Maunder Minima. An accelerator mass spectrometer(AMS) of Nagoya University was used.
We took care how high precision measurement could be achieved in preparation of samples and also in operation of AMS. We could prepare samples with high quality and uniformity by using the system constructed in this project and showed that high precision of 0.2% is achievable by evaluation of standard samples. In actual measurement overall error is determined by statistical error depending on measurement time and stability of AMS. Although the machine maintenance made it difficult to try long measurements and large target current for high precision, repeat of measurement for the same tree ring samples could realize the high precision.
We measured radiocarbon content in tree ring samples from the Maunder Minimum and the Spoerer Minimum with high precision. Analysis of time sequential data gives knowledge on variation of cosmic ray flux during the solar activity minima. It was revealed that the 11-year variation of solar activity exists even in the grand minima, however, the 11-year variation could be weak in deep minima, the cycle length, which is normally 11 years, might be possibly longer in minima, and signs of reversal of solar magnetic field are seen. We also measure radiocarbon contentin the period of around AD1000. We found a periodic structure probably due to 11-year solar activity change and discussed a possibility of the effect of supernova explosion in AD1006.
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Research Products
(12 results)
