Level and length of cyclic solar activity during the Maunder minimum as deduced from the active-day statistics
J. M. Vaquero, G. A. Kovaltsov, I. G. Usoskin, V. M. S. Carrasco and M. C. Gallego
A&A, 577 (2015) A71
Published online: 06 May 2015
(open access with registration)
Aims. The Maunder minimum (MM) of greatly reduced solar activity took place in 1645–1715, but the exact level of sunspot activity is uncertain because it is based, to a large extent, on historical generic statements of the absence of spots on the Sun. Using a conservative approach, we aim to assess the level and length of solar cycle during the MM on the basis of direct historical records by astronomers of that time.