Moving structures in ultraviolet bright points: Observations from Solar Orbiter/EUI

Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, CAS, Nanjing 210023, PR China
e-mail: lidong@pmo.ac.cn

Received: 11 December 2021
Accepted: 4 April 2022

Abstract

Context. Moving structures have been detected in coronal bright points and in a solar flare in active regions that are bidirectional, symmetrical, simultaneous, and quasi-periodic. These could be regarded as observational evidence of plasma outflows via magnetic reconnection.

Aims. We explored pairs of moving structures in fifteen ultraviolet bright points (UBPs), which were observed in the quiet Sun or inside a small active region on 19 November 2020.

Methods. The UBPs were measured by the High Resolution (HRI) Telescopes of the Extreme Ultraviolet Imager (EUI) on board the Solar Orbiter (SolO) in two passbands, HRI_EUV 174 Å and HRI_Lyα 1216 Å. The pairs of moving structures are identified in time-distance slices along curved slits of UBPs and their quasi-periods are determined from the fast Fourier transform and wavelet analysis methods.

Results. Moving structures observed in ten UBPs, starting from their bright cores and propagating toward two ends, are interpreted as diverging motions of bidirectional moving structures. These moving structures are also characterized by simultaneity and symmetry and in the case of seven UBPs, they exhibit quasi-periodicity. Moving structures seen in another five UBPs, originating from double ends, moving closer, and merging together are manifested as converging motions. A sympathetic UBP induced by the primary UBP is observed at the edge of a small active region and their moving structures also show the converging motion.

Conclusions. The diverging motions of bidirectional moving structures could be generated by outflows after magnetic reconnections. The converging motions of two moving structures might be caused by inflows through the magnetic reconnection or could also be interpreted as upflows driven by the chromospheric evaporation.