Three types of solar coronal rain during magnetic reconnection between open and closed magnetic structures

TL;DR

This study identifies and characterizes three distinct types of solar coronal rain during magnetic reconnection events between open and closed magnetic structures, using observational data from SDO and SUTRI.

Contribution

It provides the first detailed observational report of three types of coronal rain associated with interchange reconnection between open and closed magnetic fields.

Findings

Type II CR occurs during coronal condensation along reconnecting closed loops.

Type I CR involves condensation in newly-formed closed loops after reconnection.

Type III CR is associated with condensation in open structures forming magnetic dips.

Abstract

Coronal rain (CR) is a crucial part of the mass cycle between the corona and chromosphere. It includes the flare-driven CR and two types of quiescent CR separately along the non-flaring active region closed loops and along the open structures, labeled as types I, II, and III CR, respectively. Among them, types I and III CR are generally associated with magnetic reconnection. In this study, employing data taken by the Solar Dynamics Observatory (SDO) and the Solar Upper Transition Region Imager (SUTRI) on 2022 October 11, we report three types of CR during an interchange reconnection between open and closed magnetic filed structures above the southeastern solar limb. The open and closed structures converge, with the formation of current sheet at the interface, and reconnect. The newly-formed closed and open structures then recede from the reconnection region. During the reconnection, coronal condensation occurs along the reconnecting closed loops, and falls toward the solar surface along both loop legs as the type II CR. Subsequently, condensation happens in the newly-formed closed loops, and moves down toward the solar surface along both loop legs as the type I CR. Magnetic dips of the reconnecting open structures form during the reconnection. In the dips, condensation occurs, and propagates along the open structures toward the solar surface as the type III CR. Our results suggest that the reconnection rate may be crucial for the formation of types I and III CR during the reconnection.