Reciprocatory magnetic reconnection in a coronal bright point

TL;DR

This study reveals reciprocatory magnetic reconnection in a coronal bright point, showing how successive brightenings involve dynamic loop connectivity changes and interchange reconnection, advancing understanding of small-scale solar magnetic activities.

Contribution

It provides the first observational evidence of reciprocatory reconnection in a coronal bright point, demonstrating a new dynamic process in solar magnetic reconnection studies.

Findings

Repetitive brightenings in CBP involve two patches with alternating brightening order.

Large-scale coronal loop legs drift during brightenings, indicating changing magnetic connectivity.

First observational evidence of reciprocatory reconnection in a CBP.

Abstract

Coronal bright points (CBPs) are small-scale and long-duration brightenings in the lower solar corona. They are often explained in terms of magnetic reconnection. We aim to study the sub-structures of a CBP and clarify the relationship among the brightenings of different patches inside the CBP. The event was observed by the X-ray Telescope (XRT) aboard the Hinode spacecraft on 2009 August 22$-$23. The CBP showed repetitive brightenings (or CBP flashes). During each of the two successive CBP flashes, i.e., weak and strong flashes which are separated by $\sim$2 hr, the XRT images revealed that the CBP was composed of two chambers, i.e., patches A and B. During the weak flash, patch A brightened first, and patch B brightened $\sim$2 min later. During the transition, the right leg of a large-scale coronal loop drifted from the right side of the CBP to the left side. During the strong flash, patch B brightened first, and patch A brightened $\sim$2 min later. During the transition, the right leg of the large-scale coronal loop drifted from the left side of the CBP to the right side. In each flash, the rapid change of the connectivity of the large-scale coronal loop is strongly suggestive of the interchange reconnection. For the first time we found reciprocatory reconnection in the CBP, i.e., reconnected loops in the outflow region of the first reconnection process serve as the inflow of the second reconnection process.