Investigating the Behavior and Spatiotemporal Variations of Green Line Emission in the Solar Corona

TL;DR

This study analyzes green-line emissions in the solar corona across nine solar cycles, revealing latitudinal differences, associations with solar phenomena, and a 44-year hemispheric dominance cycle using advanced spectral analysis techniques.

Contribution

It provides a comprehensive multi-cycle analysis of green-line emissions, highlighting latitudinal and hemispheric variations and their relation to solar activity, which was not extensively studied before.

Findings

Higher emission activity in low latitudes (>70%)

Distinct behaviors and harmonic periods across latitudes

44-year hemispheric dominance cycle

Abstract

Understanding coronal structure and dynamics can be facilitated by analyzing green-line emission, which enables the investigation of diverse coronal structures such as coronal loops, streamers, coronal holes, and various eruptions in the solar atmosphere. In this study, we investigated the spatiotemporal behaviors of green-line emissions in both low and high latitudes across nine solar cycles, ranging from cycle 17 to the current cycle 25, using the Modified Homogeneous Data Set (MHDS). We employed methodologies such as cross-correlation, power spectral density (PSD), and wavelet transform techniques for this analysis. We found distinct behaviors in green line energy across various latitudinal distributions in the solar atmosphere. The trends observed at higher latitudes differ from those at lower latitudes. The emission behaviors show a close association with other solar phenomena like solar flares, sunspots, and coronal mass ejections (CMEs) throughout the solar cycles. The observed variations exhibit harmonic periods. The emission activity is significantly higher in the low latitudes, accounting for over 70 percent of the emissions, while the higher latitudes contribute less than 30 percent. The emissions exhibit asymmetric behavior between the northern and southern hemispheres, leading to a 44-year cycle of solar hemispheric dominance shifts. Various factors, such as Alfv\'en waves, solar magnetic fields, sunspots, differential rotation, and reconnection events, influence the observed differences in behavior between lower and higher latitudes, suggesting the existence of potential underlying phenomena contributing to deviations in properties, intensity, temporal dynamics, and spatiotemporal lifetime.