Variation of small scale magnetic fields over a century using Ca-K images as proxy

TL;DR

This study analyzes a century of Ca-K images from multiple observatories to examine small-scale magnetic features and their solar cycle variations, revealing their contribution to solar irradiance changes.

Contribution

It provides a long-term, multi-observatory analysis of small-scale magnetic features and quantifies their impact on solar irradiance over a century.

Findings

Small-scale features vary with the 11-year solar cycle.

Feature areas range from 5% to 20% of the solar surface.

Small features contribute about 3% to solar irradiance variation.

Abstract

A combined uniform and long-time series of Ca-K images from the Kodaikanal Observatory (KO), Mount Wilson Observatory (MWO), and Mauna Loa Solar Observatory (MLSO) were used to identify and study the Ca-K small-scale features and their solar cycle variations over a century. The small scale features are classified into three distinct categories: enhanced network (EN), active network (AN), and quiet network (QN). All these features show that their areas vary according to the 11-year solar cycle. The relative amplitude of the Ca-K network variations agree with that of the sunspot cycle. The total area of these small-scale features varies from about 5% during the minimum phase of the solar cycle to about 20% during its maximum phase. Considering the average intensity and the amplitude of their area variations, we find that the total contribution of EN, AN and QN to the irradiance variation of the Sun is about 3%.