The nature of the solar activity during the Maunder Minimum revealed by the Guliya ice core record

Whether the solar activity was very low, and especially whether the solar cycle existed, during the Maunder Minimum (1645–1715 AD), have been disputed for a long time. In this paper we use the Guliya NO₃ ⁻ data, which can reflect the solar activity, to analyze the characteristics of the solar activity during the Maunder Minimum. The results show that the solar activity was indeed low, and solar cycle displayed normal as present, i.e. about 11a, in that period. Moreover, it was found that the solar activity contains a 36-year periodic component probably, which might be related to the variations in the length of the sunspot cycle. This finding is of importance for the study of the relationship between the sun variability and the Earth climate change.