Understanding of the periodicity of the past solar activity by radiocarbon measurements and the relation to the global environment

我们测量了过去3,000年来树木年轮中的放射性碳浓度，并讨论了过去宇宙射线强度和太阳活动的变化。发现在太阳活动变化的特征时期--太阳活动大极小期，Schwabe周期长度从现代的11年增加到13-16年。我们还发现在AD 775和AD 993处放射性碳浓度迅速增加。这些事件表明，近几年来太阳表面发生了极大的耀斑，大量的太阳高能粒子到达了地球环境。这些结果对于解决太阳活动的发电机机制及其对地球影响的认识具有重要意义。

We have measured the radiocarbon concentration in tree rings from the past 3,000 years and discussed the variation of cosmic-ray intensity and solar activity in the past. We found the increase of theSchwabe cycle lengths from the modern value of 11 years to 13-16 years during grand solar minima, which are characteristic periods of solar activity change. We also discovered the rapid increase of radiocarbon concentration at AD775 and AD993. These events indicate that extremely large solar flares occurred at the solar surface in these yearsand a lot of solar high-energy particles arrived at the global environment. These results largely contribute to solve the dynamo mechanism of solar activity and the understanding of its influence to the Earth.