Formation of Large Scale Coronal Loops Interconnecting Two Active Regions Through Gradual Magnetic Reconnection and Associated Heating Process

TL;DR

This study details the formation of large-scale interconnecting coronal loops between active regions via gradual magnetic reconnection high in the corona, highlighting the heating process responsible for their brightening in X-ray and EUV wavelengths.

Contribution

It provides the first comprehensive observational analysis of IL formation through high-altitude reconnection and associated heating, clarifying their formation mechanism and energy release process.

Findings

ILs form through gradual high-coronal reconnection

IL brightening results from direct heating at reconnection sites

Supports IL formation theories with observational evidence

Abstract

Coronal loops interconnecting two active regions, called as interconnecting loops (ILs), are prominent large-scale structures in the solar atmosphere. They carry a significant amount of magnetic flux, therefore are considered to be an important element of the solar dynamo process. Earlier observations show that eruptions of ILs are an important source of CMEs. It is generally believed that ILs are formed through magnetic reconnection in the high corona (>150-200"), and several scenarios have been proposed to explain their brightening in soft X-rays (SXRs). Yet, the detailed IL formation process has not been fully explored and the associated energy release in the corona still remains unresolved. Here we report the complete formation process of a set of ILs connecting two nearby active regions, with successive observations by STEREO-A on the far side of the Sun and SDO and Hinode on the Earth side. We conclude that ILs are formed by gradual reconnection high in the corona, in line with earlier postulations. In addition, we show evidence supporting that ILs become brightened in SXRs and EUVs through heating at or close to the reconnection site in the corona (i.e., through direct heating process of reconnection), a process that has been largely overlooked in earlier studies on ILs