Width of Sunspot Generating Zone and Reconstruction of Butterfly Diagram

TL;DR

This paper demonstrates that the latitudinal width of the sunspot generating zone correlates with solar activity levels, allowing reconstruction of historical butterfly diagrams from sunspot data.

Contribution

It introduces a method to relate sunspot zone width to activity levels and reconstructs historical butterfly diagrams using sunspot group data.

Findings

Sunspot zone width expands with increased solar activity.

The ratio of sunspot number to zone width saturates at high activity levels.

Historical butterfly diagrams can be reconstructed from sunspot data.

Abstract

Based on the extended Greenwich-NOAA/USAF catalogue of sunspot groups it is demonstrated that the parameters describing the latitudinal width of the sunspot generating zone (SGZ) are closely related to the current level of solar activity, and the growth of the activity leads to the expansion of SGZ. The ratio of the sunspot number to the width of SGZ shows saturation at a certain level of the sunspot number, and above this level the increase of the activity takes place mostly due to the expansion of SGZ. It is shown that the mean latitudes of sunspots can be reconstructed from the amplitudes of solar activity. Using the obtained relations and the group sunspot numbers by Hoyt and Schatten (1998), the latitude distribution of sunspot groups ("the Maunder butterfly diagram") for the 18th and the first half of the 19th centuries is reconstructed and compared with historical sunspot observations.