Network and Plage Indices from Kodaikanal Ca-K Data

TL;DR

This paper analyzes Ca II K solar images from Kodaikanal Observatory to quantify chromospheric network and plage activity, revealing their correlation with the solar cycle and hemispheric asymmetries.

Contribution

Developed programs to extract network and plage indices from daily Ca-K images, providing new insights into solar activity patterns and hemispheric differences.

Findings

Network and plage indices follow the solar cycle.

A secondary peak occurs during declining activity.

Northern hemisphere is more active than the southern in network indices.

Abstract

The Ca II K filtergrams from Kodaikanal Solar Observatory have been used to study the solar activity. The images are dominated by the chromospheric network and plages. Programs have been developed to obtain the network and plage indices from the daily images as functions of solar latitude and time. Preliminary results from the analysis are reported here. The network and plage indices were found to follow the sunspot cycle. A secondary peak is found during the declining activity period in both the indices. A comparison of network indices from the northern and the southern hemispheres shows that the former is more active than latter. However such an asymmetry is not clearly seen in the case of plage index.