Latitude Distribution of Sunspots: Analysis Using Sunspot Data and A Dynamo Model

TL;DR

This study analyzes sunspot latitude distributions over multiple solar cycles, revealing hemispheric asymmetries and correlations with cycle strength, and confirms these features using a flux transport dynamo model with stochastic fluctuations.

Contribution

It introduces a detailed analysis of sunspot latitude evolution and demonstrates that a flux transport dynamo model can replicate observed distribution features and their cycle-dependent variations.

Findings

Sunspot distributions propagate toward the equator during cycles.

Distribution parameters correlate with cycle strength and show hemispheric asymmetries.

The dynamo model reproduces observed distribution features and their evolution.

Abstract

In this paper, we explore the evolution of sunspot latitude distribution and explore its relations with the cycle strength. With the progress of the solar cycle, the distributions in two hemispheres from mid-latitudes propagate toward the equator and then (before the usual solar minimum) these two distributions touch each other. By visualizing the evolution of the distributions in two hemispheres, we separate the solar cycles by excluding this hemispheric overlap. From these isolated solar cycles in two hemispheres, we generate latitude distributions for each cycle, starting from cycle 8 to cycle 23. We find that the parameters of these distributions, namely, the central latitude ($C$), width ($\delta$) and height ($H$) evolve with the cycle number and they show some hemispheric asymmetries. Although the asymmetries in these parameters persist for a few successive cycles, they get corrected within a few cycles and the new asymmetries appear again. In agreement with the previous study, we find that distribution parameters are correlated with the strengths of the cycles, although these correlations are significantly different in two hemispheres. The general trend that stronger cycles begin sunspot eruptions at relatively higher latitudes and have wider bands of sunspot emergence latitudes are confirmed when combining the data from two hemispheres. We explore these features using a flux transport dynamo model with stochastic fluctuations. We find that these features are correctly reproduced in this model. The solar cycle evolution of the distribution center is also in good agreement with observations. Possible explanations of the observed features based on this dynamo model are presented.