Oscillatory magnetic reconnection at a coronal bright point

TL;DR

This study provides the first observational evidence of oscillatory magnetic reconnection at a coronal bright point, revealing a dynamic process involving current sheet formation, reversal, and brightness modulation in the solar corona.

Contribution

It reports the first direct observation of oscillatory magnetic reconnection at a coronal bright point using high-resolution EUV images, highlighting the process's dynamics and its effect on brightness.

Findings

Identification of two bursty reconnection phases with a reversal.

Observation of current sheet formation, shortening, and null point transition.

Reconnection modulates the brightness of the coronal bright point.

Abstract

Coronal bright points are typical small-scale coronal brightenings that consist of a bundle of miniature coronal loops. Using the ultra-high-resolution coronal images from the Extreme Ultraviolet Image onboard Solar Obiter, we report the first observational evidence of oscillatory magnetic reconnection at a coronal bright point (CBP). The reconnection is characterised by two bursty phases defined by a reconnection reversal. In the first phase, a current sheet (C1) is found to form in front of an expanding loop of the bright point. Interestingly, C1 shorten to a null point during 10 minutes after reaching its maximum length (~2.4Mm). Less than 3 minutes later, a new current sheet (C2) was clearly seen to grow out from the null point, but along an orthogonal direction relative to C1. C2 reached a maximum length of ~4 Mm in ten minutes and then has become short and invisible in the next few minutes as the reconnection has declined. The magnetic reconnection is evidenced by the brightening, plasma flow and temperature increase at the ends of both C1 and C2. No significant magnetic cancellation or emergence but gradual convergence has occurred during a few hours before the reconnection underneath the CBP. The transition from C1 to C2 suggests the occurrence of coronal oscillatory reconnection with once reconnection reversal, whereby the inflow and outflow regions in the first phase become the outflow and inflow regions in the second phase, respectively. It is further found that the oscillatory reconnection could slightly modulate the change in brightness of the coronal bright point.