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

为了研究近千年来太阳活动的变化，测量了雅库茨克雪松年轮中的放射性碳浓度。到目前为止，我们已经制作了样品，并测量了太阳活动降低时斯波雷尔极小期的放射性碳浓度。将AD 1410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AD 1480至1530样品，由于没有获得足够量的高纯度苯，因此用加速器质谱法（AMS）测量放射性碳活性。LSC法需要100克木材样品才能达到良好的统计准确度，而AMS法只需10 mg。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0.2%到0.3%的精度，但作为第一步，我们的测量精度相当差。到目前为止，我们已经测量了AD 1410到1480的几乎所有年度样品和AD 1480到1530的每两个年度样品的放射性碳含量。用两种方法对部分样品进行了测定，在误差范围内得到了相同的活性。我们的结果与Stuiver的北美树木年轮放射性碳含量年代际变化趋势一致，去除长期趋势后，我们的结果变化在± 0.5%以内。这与Kocharov关于蒙德极小期的树轮的结果不同。用最大熵方法对谱密度的周期性进行了分析，发现谱密度的一个主要峰值出现在21年。这与蒙德极小期的趋势相同。太阳和行星际空间在大极小期可能具有不同的磁性机制和结构。

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.