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

TL;DR

This study comprehensively reassesses multiple datasets and evidence to confirm that solar activity during the Maunder minimum (1645-1715) was exceptionally low, significantly lower than recent solar cycles.

Contribution

It provides a thorough reevaluation of diverse direct and indirect data sources, conclusively establishing the Maunder minimum as a period of very low solar activity.

Findings

Solar activity was at an exceptionally low level during the Maunder minimum.

Claims of moderate or high activity during this period are strongly rejected.

The Maunder minimum's solar activity was lower than the Dalton minimum and current solar cycle #24.

Abstract

Aims: Although the time of the Maunder minimum (1645--1715) is widely known as a period of extremely low solar activity, claims are still debated that solar activity during that period might still have been moderate, even higher than the current solar cycle #24. We have revisited all the existing pieces of 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 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 data sets. 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 below that during the Dalton minimum 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 at a high confidence level.