Magnetic Flux Emergence in a Coronal Hole

TL;DR

This study investigates magnetic flux emergence in a coronal hole using multi-instrument observations, revealing how flux patches influence the coronal hole's area and magnetic structure, with implications for solar wind properties.

Contribution

It provides detailed analysis of flux emergence and cancellation in a coronal hole and their effects on its evolution, combining data from multiple space and ground-based observatories.

Findings

Flux emergence patches erode the coronal hole area.

Flux cancellation increases the coronal hole area.

Coronal hole evolution affects solar wind parameters.

Abstract

A joint campaign of various space-borne and ground-based observatories, comprising the Japanese Hinode mission (HOP~338, 20\,--\,30~September 2017), the GREGOR solar telescope, and the \textit{Vacuum Tower Telescope} (VTT), investigated numerous targets such as pores, sunspots, and coronal holes. In this study, we focus on the coronal hole region target. On 24~September 2017, a very extended non-polar coronal hole developed patches of flux emergence, which contributed to the decrease of the overall area of the coronal hole. These flux emergence patches erode the coronal hole and transform the area into a more quiet-Sun-like area, whereby bipolar magnetic structures play an important role. Conversely, flux cancellation leads to the reduction of opposite-polarity magnetic fields and to an increase in the area of the coronal hole. Other global coronal hole characteristics, including the evolution of the associated magnetic flux and the aforementioned area evolution in the EUV, are studied using data of the \textit{Helioseismic and Magnetic Imager} (HMI) and \textit{Atmospheric Imaging Assembly} (AIA) onboard the \textit{Solar Dynamics Observatory} (SDO). The interplanetary medium parameters of the solar wind display parameters compatible with the presence of the coronal hole. Furthermore, a particular transient is found in those parameters.