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.

为了研究上一个千年中太阳能活性的变化，已经测量了Yaku Ceder树环中放射性碳的浓度。到目前为止，当降低太阳活性时，我们已经生产了样品并测量了spoerer最小的放射性碳的浓度。将AD1410至1480的纤维素样品转化为苯，并通过液体闪烁（LSC）方法测量放射性碳活性。对于AD1480至1530的样品，由于未获得足够量的高纯度苯，因此通过加速器质谱（AMS）测量了放射线活性。虽然需要一百克木材样品才能实现LSC方法良好的统计准确性，但仅10 mg就足以容纳AMS方法。目前，LSC方法的可获得精度为0.3至0.4％，AMS方法的可获得精度为0.4至0.5％。尽管我们的最终目标是准确性为0.2％至0.3％，但我们的准确性较差，直到第一步。现在，已经测量了几乎所有年度AD1410至1480年的样本的放射性碳含量，并且每年的每年的AD1480至1530年级样本都可以通过两种方法来测量这些方法。我们的结果与Stuiver在北美树环中折叠式放射性碳含量非常吻合。我们的放射性碳含量的变化在删除长期趋势后的变化在±0.5％以内。这与Kocharov的Maunder最低限度的树环的结果不同。我们通过MEM方法分析的周期性分析显示了21年的光谱密度的主要峰。这与Maunder最低限度获得的趋势相同。太阳和星际空间可能具有不同的磁性机理和结构。