Solar coronal loop dynamics near the null point above active region NOAA 2666

TL;DR

This study observes a saddle-like coronal structure above active region NOAA 2666, demonstrating magnetic reconnection without heating signatures, and confirms the presence of a null point with a fan-spine magnetic configuration.

Contribution

It provides detailed observational evidence of magnetic reconnection at a null point in the solar corona with a fan-spine topology, supported by magnetic field modeling.

Findings

Coronal loops converged vertically and diverged horizontally during reconnection.

No heating signatures were observed in the reconnection region.

Magnetic field modeling confirmed a null point at 122" height with a fan-spine configuration.

Abstract

We analyse observations of a saddle-like structure in the corona above the western limb of the Sun on 2017 July 18. The structure was clearly outlined by coronal loops with typical coronal temperature no more than 1 MK. The dynamics of loops showed convergence toward the centre of the saddle in the vertical direction and divergence in the horizontal direction. The event is a clear example of smooth coronal magnetic field reconnection. No heating manifestations in the reconnection region or magnetically connected areas were observed. Potential magnetic field calculations, which use as the boundary condition the SDO/HMI magnetogram taken on July 14, showed the presence of a null point at the height of 122" above the photosphere just at the centre of the saddle structure. The shape of field lines fits the fan-spine magnetic configuration above NOAA 2666.