Level and length of cyclic solar activity during the Maunder minimum as deduced from the active-day statistics
J. M. VaqueroDepartamento de FísicaUniversidad de Extremadura, 06800 Mérida, SpainG. A. KovaltsovIoffe Physical-Technical Institute, 194021 St. Petersburg, RussiaI. G. UsoskinSodankylä Geophysical Observatory and ReSoLVE Center of Excellence, University of Oulu, 90014 Oulu, FinlandV. M. S. CarrascoDepartamento de Física, Universidad de Extremadura, 06071 Badajoz, SpainM. C. GallegoDepartamento de Física, Universidad de Extremadura, 06071 Badajoz, Spain
2015en
ABI
Abstract
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.
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