A Revised Collection of Sunspot Group Numbers

TL;DR

This paper presents a revised and expanded collection of sunspot group numbers from 1610 to present, improving data accuracy and providing a reliable index of solar activity during the Maunder Minimum.

Contribution

It introduces a revised sunspot group dataset with significant data corrections and includes a new index of solar activity during the Maunder Minimum, based on this improved collection.

Findings

Increased solar activity levels during the Maunder Minimum compared to previous data.

Elimination of many observations during the Maunder Minimum enhances data reliability.

The new dataset is publicly available in digital format.

Abstract

We describe a revised collection of the number of sunspot groups from 1610 to the present. This new collection is based on the work of Hoyt and Schatten (Solar Phys. 179, 189, 1998). The main changes are the elimination of a considerable number of observations during the Maunder Minimum (hereafter, MM) and the inclusion of several long series of observations. Numerous minor changes are also described. Moreover, we have calculated the active-day percentage during the MM from this new collection as a reliable index of the solar activity. Thus, the level of solar activity obtained in this work is greater than the level obtained using the original Hoyt and Schatten data, although it remains compatible with a grand minimum of solar activity. The new collection is available in digital format.