Revisiting the formation mechanism for coronal rain from previous studies

TL;DR

This study revisits the formation mechanisms of quiescent coronal rain, highlighting the role of interchange magnetic reconnection between open and closed magnetic field lines in its development.

Contribution

It provides a detailed analysis of 15 quiescent coronal rain events, demonstrating that 40% can be explained by interchange reconnection mechanisms, thus emphasizing its significance.

Findings

40% of studied events explained by interchange reconnection

Interchange reconnection plays a significant role in coronal rain formation

Revisiting previous reports supports the importance of magnetic reconnection

Abstract

Solar coronal rain is classified generally into two categories: flare-driven and quiescent coronal rain. The latter is observed to form along both closed and open magnetic field structures. Recently, we proposed that some of the quiescent coronal rain events, detected in the transition region and chromospheric diagnostics, along loop-like paths could be explained by the formation mechanism for quiescent coronal rain facilitated by interchange magnetic reconnection between open and closed field lines. In this study, we revisited 38 coronal rain reports from the literature. From these earlier works, we picked 15 quiescent coronal rain events out of the solar limb, mostly suggested to occur in active region closed loops due to thermal nonequilibrium, to scrutinize their formation mechanism. Employing the extreme ultraviolet images and line-of-sight magnetograms, the evolution of the quiescent coronal rain events and their magnetic fields and context coronal structures is examined. We find that 6, comprising 40%, of the 15 quiescent coronal rain events could be totally or partially interpreted by the formation mechanism for quiescent coronal rain along open structures facilitated by interchange reconnection. The results suggest that the quiescent coronal rain facilitated by interchange reconnection between open and closed field lines deserves more attention.