Long-lived sunspots in historical records: a case study analysis from 1660 to 1676

TL;DR

This study analyzes 17th-century sunspot records to assess the longevity and characteristics of sunspots during the Maunder minimum, revising previous hypotheses and providing insights into solar rotation and activity.

Contribution

It offers a detailed re-evaluation of historical sunspot data, challenging prior assumptions about long-lived sunspots and their implications for solar convection during the Maunder minimum.

Findings

Long-lived sunspots were present during 1660-1676.

Historical rotation profiles match modern long-lived sunspot groups.

Revised understanding of sunspot longevity and solar activity during the Maunder minimum.

Abstract

Sunspot engravings and measurements in 1660-1676 are analyzed to retrieve sunspot area and heliocoordinates. Based on these data, we revise the Hoyt and Schatten (The role of the sun in climate change, 1997) hypothesis of long-lived sunspots during the Maunder minimum as a sign of weakened convection. Historical reports also clarify what each observer defined as a sunspot and the purpose of the observations. The reconstructed longitudes of sunspots allow us to evaluate the rotation rate, revealing that the historical rotation profile resembles that of long-lived sunspot groups in the modern era.