Association of Plages With Sunspots: A multi wavelength Study Using Kodaikanal Ca $\scriptsize{{\textrm{II}}}$ K and Greenwich sunspot area Data

TL;DR

This study investigates the relationship between chromospheric plages and photospheric sunspots using multi-wavelength data, revealing strong correlations in their areas, distributions, and cycle properties, and identifying size thresholds for association.

Contribution

First to compare individual plage areas with sunspot areas over time, providing new insights into magnetic structure associations across solar atmospheric layers.

Findings

Plages and sunspots are highly correlated over the solar cycle.

Plages with area ≥4 arcmin² are mostly associated with sunspots.

Different plage sizes show varying cyclic properties.

Abstract

Plages are the magnetically active chromospheric structures prominently visible in Ca $\scriptsize{{\textrm{II}}}$ K line (3933.67 \r{A}). A plage may or may not be associated with a sunspot which is a magnetic structure visible in the solar photosphere. In this study we explore this aspect of association of plages with sunspots using the newly digitized Kodaikanal Ca $\scriptsize{{\textrm{II}}}$ K plage data and the Greenwich sunspot area data. Instead of using the plage index or fractional plage area and their comparison with the sunspot number, we use, to our knowledge for the first time, the individual plage areas and compared it with the sunspot area time series. Our analysis shows that these two structures formed at two different layers are highly correlated with each other on a time scale comparable to the solar cycle. The area and the latitudinal distributions of plages are also similar to that of the sunspots. Different area thresholdings on the `Butterfly diagram' reveal that plages with area $\geq$4 arcmin$^2$ are mostly associated with a sunspot in the photosphere. Apart from this, we found that the cyclic properties change when different sized plages are considered separately. These results may help us to better understand the generation and the evolution of the magnetic structures in different layers of the solar atmosphere.