Revisited sunspot data: A new scenario for the onset of the Maunder minimum

TL;DR

This study revises sunspot data before the Maunder Minimum, suggesting a gradual onset of reduced solar activity two cycles prior, which impacts theories of long-term solar dynamo behavior.

Contribution

It introduces newly recovered and revised sunspot observations that significantly alter the understanding of the Maunder Minimum's onset, challenging previous paradigms.

Findings

Revised sunspot cycle magnitude from 60-70 to about 20 before the Maunder Minimum.

Indicates a gradual decline in solar activity starting two cycles prior.

Changes the observational constraints for solar dynamo theories.

Abstract

Maunder Minimum forms an archetype for the Grand minima, and detailed knowledge of its temporal development has important consequences for the solar dynamo theory dealing with long-term solar activity evolution. Here we reconsider the current paradigm of the Grand minimum general scenario by using newly recovered sunspot observations by G. Marcgraf and revising some earlier uncertain data for the period 1636--1642, i.e., one solar cycle before the beginning of the Maunder Minimum. The new and revised data dramatically change the magnitude of the sunspot cycle just before the Maunder Minimum, from 60--70 down to about 20, implying a possibly gradual onset of the Minimum with reduced activity started two cycles before it. This revised scenario of the Maunder Minimum changes, through the paradigm for Grand solar/stellar activity minima, the observational constraint on the solar/stellar dynamo theories focused on long-term studies and occurrence of Grand minima.