Schwabe Solar Cycle in 1000–1700: Variations in Length and Amplitude

Abstract

One of the most significant features of solar activity is its variability in a wide range of periods with the dominance of the 11-year cycle or the Schwabe cycle. In this article, a wavelet analysis of solar activity data for 1000–1700 obtained using the number of auroras taking into account the contribution of the geomagnetic field taken into account is performed. The results show the stable presence of an 11-year cycle throughout 1000–1700. It is found that there is a systematic increase in the Schwabe cycle length in 1000–1350, after which its decrease is observed. At the same time, the length of the solar cycle increases during the Oort (13 years), Wolf (14 years), and Spörer (14–15 years) grand minima. It is established that the correlation between the amplitude and length of the solar cycle was preserved over the entire time interval of 1000–1700, but its sign changed. It is also found that the correlation between the amplitude of the cycle and the length of the previous cycle is stronger than the correlation between the amplitude and the length of the same cycle. This result is similar to what is known previously for instrumental series. However, we show that this pattern persists over a much longer time interval, and it does not depend on the sign of the correlation. The article also provides indications of the existence of solar activity variations in 1000–1550 with a period of 30–40 years.