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Study of the solar activity in the past by measurement of radiocarbon in tree rings

通过测量树木年轮中的放射性碳来研究过去的太阳活动

基本信息

批准号：
12440062
负责人：
MASUDA Kimiaki
金额：
$ 10.43万
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：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-12440062/
关键词：
Solar activity Cosmic ray Radiocarbon Spoerer minimum Liquid scintillator Accelerator mass spectrometer Climate change Maunder minimum 放射線計測同位体効果

项目摘要

In order to investigate the variability of solar activity in the last millenium, the concentrations of radiocarbon in Yaku ceder tree rings have been measured. Until now, we have produced samples and measured the concentration of radiocarbon for the Spoerer minimum when the solar activity was lowered. The cellulose samples of AD1410 to 1480 were converted to benzene and radiocarbon activity was measured by the liquid scintillation (LSC) method. For the samples of AD1480 to 1530, radiocrbon activity was measured by the accelerator mass spectometry (AMS) because enough amount of benzene with high purity was not obtained. While a hundred gram of wood samples are necessary for good statistical accuracy for LSC method, only 10 mg is sufficient for AMS method. At present, obtainable accuracy is 0.3 to 0.4 % for LSC method and 0.4 to 0.5 % for AMS method. Although our final goal is the accuracy of 0.2 to 0.3 %, we have measured in rather worse accuracy as a first step.Until now, radiocarbon contents have been measured for almost all yearly samples of AD1410 to 1480 and for every wo year samples of AD1480 to 1530. Some samples were measured by the both method and the same activity was obtained within the error. Our results agrees well with the decadal radiocarbon contents in tree rings of North America by Stuiver.The variation of our radiocarbon contents is within ±0.5 % after removing the long term trend. This differ from the result for the tree rings of the Maunder minimum by Kocharov. Our periodicity analysis by MEM method shows a dominat peak of spectral density at 21 year. This is the same trend as that obtained for the Maunder minimum. The sun and interplanetary space might have different mechanism and structure of magnetism in the grand minima.

为了研究过去一千年太阳活动的变化，对雅库雪松年轮中的放射性碳浓度进行了测量。到目前为止，我们已经制作了样品，并测量了太阳活动减弱时斯波尔极小期的放射性碳浓度。将AD1410 ~ 1480的纤维素样品转化为苯，用液体闪烁（LSC）法测定其放射性碳活度。对于AD1480 ~ 1530样品，由于没有获得足够量的高纯度苯，采用加速器质谱（AMS）测定放射性碳活度。LSC法需要100克木材样品才能达到良好的统计精度，而AMS法仅需10毫克即可。目前，LSC法的准确度为0.3 ~ 0.4%，AMS法的准确度为0.4 ~ 0.5%。虽然我们的最终目标是准确度达到0.2 - 0.3%，但我们第一步测量的准确度相当差。到目前为止，已经测量了几乎所有AD1410至1480的年度样品和AD1480至1530的每两年样品的放射性碳含量。用两种方法测定了一些样品，在误差范围内得到了相同的活度。结果与史岱佛测定的北美树木年轮年代际放射性碳含量吻合较好。除去长期趋势后，我们的放射性碳含量变化在±0.5%以内。这与Kocharov对蒙德极小值的树轮结果不同。用MEM方法进行的周期性分析表明，谱密度在21年出现一个主峰。这与蒙德极小值的趋势相同。太阳和行星际空间在极小期可能具有不同的磁性机制和结构。