The Maunder minimum (1645–1715) was indeed a grand minimum: A reassessment of multiple datasets

¹ ReSoLVE Centre of Excellence, University of Oulu, 90014, Finland
² Sodankylä Geophysical Observatory, University of Oulu, 90014, Finland
³ Leibniz Institute for Astrophysics Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
⁴ Ioffe Physical-Technical Institute, 194021 St. Petersburg, Russia
⁵ Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
⁶ Department of Meteorology, University of Reading, UK
⁷ ReSoLVE Centre of Excellence, Department of Computer Science, PO BOX 15400, Aalto University, 00076 Aalto, Finland
⁸ Moscow State University, 119991 Moscow, Russia
⁹ IZMIRAN, Moscow, Russia
¹⁰ School of Space Research, Kyung Hee University, Yongin, 446-701 Gyeonggi, Republic of Korea
¹¹ Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA
¹² Departamento de Física, Universidad de Extremadura, Mérida (Badajoz), 10003 Cáceres, Spain

Received: 2 June 2015
Accepted: 12 July 2015

Abstract

Aims. Although the time of the Maunder minimum (1645–1715) is widely known as a period of extremely low solar activity, it is still being debated whether solar activity during that period might have been moderate or even higher than the current solar cycle #24. We have revisited all existing evidence and datasets, both direct and indirect, to assess the level of solar activity during the Maunder minimum.

Methods. We discuss the East Asian naked-eye sunspot observations, the telescopic solar observations, the fraction of sunspot active days, the latitudinal extent of sunspot positions, auroral sightings at high latitudes, cosmogenic radionuclide data as well as solar eclipse observations for that period. We also consider peculiar features of the Sun (very strong hemispheric asymmetry of the sunspot location, unusual differential rotation and the lack of the K-corona) that imply a special mode of solar activity during the Maunder minimum.

Results. The level of solar activity during the Maunder minimum is reassessed on the basis of all available datasets.

Conclusions. We conclude that solar activity was indeed at an exceptionally low level during the Maunder minimum. Although the exact level is still unclear, it was definitely lower than during the Dalton minimum of around 1800 and significantly below that of the current solar cycle #24. Claims of a moderate-to-high level of solar activity during the Maunder minimum are rejected with a high confidence level.