Characteristics of latitude distribution of sunspots and their links to solar activity in pre-Greenwich data

TL;DR

This study compares sunspot latitude distributions in pre-Greenwich data, revealing stable links with solar activity and proposing methods to assess data quality and normalize activity levels in historical observations.

Contribution

It demonstrates the stability of sunspot latitude properties against data loss and identifies potential errors in early Schwabe data, enhancing historical solar activity analysis.

Findings

Latitude dispersion correlates with solar cycle amplitude.

Sunspot latitude properties are more stable than amplitude indices.

Schwabe data may contain latitude determination errors.

Abstract

We study and compare characteristics of sunspot group latitude distribution in two catalogs: the extended Greenwich (1874--2014) and Schwabe ones (1825--1867). We demonstrate that both datasets reveal similar links between latitude and amplitude characteristics of the 11-year cycle: the latitude dispersion correlates with the current activity and the mean latitude of sunspots in the cycle's maximum is proportional to its amplitude, It agrees with conclusions that we made in previous papers for the Greenwich catalog. We show that the latitude properties of sunspot distribution are much more stable against loss of observational data than traditional amplitude indices of activity. Therefore, the found links can be used for estimates of quality of observations and independent normalizing of activity levels in a gappy pre-Greenwich data. We demonstrate it using the Schwabe catalog as an example. In addition, we show that the first part of the Schwabe data probably contains errors in determination of sunspot latitudes that lead to overestimation of the sunspot latitude dispersions.