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A study of the solar activity variability in the past millennium by precise radiocarbon measurement

通过精确的放射性碳测量研究过去千年太阳活动的变化

基本信息

批准号：
14340071
负责人：
MASUDA Kimiaki
金额：
$ 9.41万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14340071/
关键词：
Radiocarbon Solar activity Accelerator Mass spectrometry Cosmic rays The Maunder Minimum The Spoerer Minimum Little Ice Age Climate change 液体シンチレーション

项目摘要

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.

该项目的目的是利用加速器质谱仪在太阳活动极大极小期期间通过树木年轮中的放射性碳来研究过去一千年太阳活动的变化和行星际磁场的结构。为此，我们准备了样品，并非常小心地测量了放射性碳含量，并试图找到斯波雷尔和蒙德极小值中放射性碳含量的微小变化。使用了名古屋大学的加速器质谱仪（AMS），在样品的制备和AMS的操作中，注意了如何实现高精度的测量。利用本项目所建立的系统，可以制备出高质量、均匀的样品，并通过对标准样品的评价，表明其精密度可达到0.2%。在实际测量中，总误差取决于测量时间和AMS稳定性的统计误差。虽然由于机器维护的原因，很难进行长时间的测量和大靶电流的高精度测量，但对同一年轮样品进行重复测量可以实现高精度测量。我们对蒙德极小期和斯波雷极小期的树木年轮样品进行了高精度的放射性碳含量测量。对时间序列数据的分析提供了关于太阳活动极小期宇宙射线通量变化的知识。结果表明，太阳活动在大极小期也存在11年变化，而在深极小期11年变化可能较弱，极小期的周期长度可能较长，通常为11年，并有太阳磁场反转的迹象。我们还测量了大约公元1000年期间的放射性碳含量。我们发现了一个周期性的结构，可能是由于11年的太阳活动变化，并讨论了在AD 1006超新星爆发的影响的可能性。