A Statistical Analysis of Solar Surface Indices Through the Solar Activity Cycles 21-23

TL;DR

This study analyzes solar surface indices across solar activity cycles 21-23, revealing correlations between sunspot group sizes and surface features, and offering insights into solar activity trends and their impact on solar irradiance.

Contribution

It provides a detailed statistical analysis of solar surface indices and their relation to sunspot group sizes during multiple solar cycles, using Python-based time series analysis.

Findings

Strong correlation between small and large sunspot groups and surface indices.

Plage regions decreased despite more large sunspot groups in cycle 23.

Facular areas increased, causing minor TSI decrease, while plage area decline led to magnetic field reduction.

Abstract

Variations of total solar irradiance (TSI), magnetic field, Ca II K-flux, faculae and plage areas due to the number and the type of sunspots/sunspot groups (SGs) are well established by using Solar Irradiance Platform and ground based data from various centers such as Stanford Data (SFO), Kodaikanal data (KKL) and National Geographical Data Center (NGDC) Homepage, respectively. We applied time series analysis for extracting the data over the descending phases of solar activity cycles (SACs) 21, 22 and 23, and the ascending phases 22 and 23 of SACs, and analyzed the selected data using the Python programming language. Our detailed analysis results suggest that there is a stronger correlation between solar surface indices and the changes in the relative portion of the small and large SGs. This somewhat unexpected finding suggest that plage regions decreased in a lower values in spite of the higher number of large SGs in SAC 23 while Ca II K-flux did not decrease by large amount or it was comparable with SAC 22 for some years and relates with C type and DEF type SGs. Thus, increase of facular areas which are influenced by large SGs caused a small percentage decrease in TSI while decrement of plage areas triggered a higher decrease in the flux of magnetic field. Our results thus reveal the potential of such detailed comparison of SG analysis with solar surface indices for understanding and predicting future trends in the SAC.