Cyclic behaviour of sunspot activity during the Maunder minimum

Abstract

We study the behaviour of sunspot activity in 1610- 1750, i.e. just prior to, during and slightly after the Maun- der minimum, using the new series of group sunspot numbers (Hoyt & Schatten 1998). We apply the delayed component tech- nique and show that, while the transition from the normal cyclic evolution to the minimum was very abrupt, the recovery from the minimum was gradual, proceeding through a tiny but very regular cycle in 1700-1712 and a transition period with a phase catastrophe in 1712-1720. Exploiting the good coverage of the Maunder minimum by daily solar observations, we show that the sunspot ocurrence is concentrated, with a high statistical significance, to two intervals around 1658 and 1680. Together with the last sunspot maximum before the Maunder minimum in 1639/1640, and the maximum in 1705, this implies a sig- nificant, approximately 22-year periodicity in sunspot activity during the Maunder minimum. entire GSN interval except for MM. In this paper, we perform a detailed analysis of SA using GSN data for the years 1610- 1750, covering the time slightly before and after MM, as well as the minimum time itself. Using the delayed component method, we study the phase space evolution of solar cycles around the MM. Also, we examine the question whether the remnant ac- tivity during the minimum is sporadic or regular by analyzing the distribution of days with registered sunspots. 2. Phase evolution of sunspot activity cycles