  We report on the merging between the southern polar coronal hole and an
adjacent coronal dimming induced by a coronal mass ejection on 2022 March 18,
resulting in the merged region persisting for at least 72 hrs. We use remote
sensing data from multiple co-observing spacecraft to understand the physical
processes during this merging event. The evolution of the merger is examined
using Extreme-UltraViolet (EUV) images obtained from the Atmospheric Imaging
Assembly onboard the Solar Dynamic Observatory and Extreme Ultraviolet Imager
onboard the Solar Orbiter spacecraft. The plasma dynamics are quantified using
spectroscopic data obtained from the EUV Imaging Spectrometer onboard Hinode.
The photospheric magnetograms from the Helioseismic and Magnetic Imager are
used to derive magnetic field properties. To our knowledge, this work is the
first spectroscopical analysis of the merging of two open-field structures. We
find that the coronal hole and the coronal dimming become indistinguishable
after the merging. The upflow speeds inside the coronal dimming become more
similar to that of a coronal hole, with a mixture of plasma upflows and
downflows observable after the merging. The brightening of bright points and
the appearance of coronal jets inside the merged region further imply ongoing
reconnection processes. We propose that component reconnection between the
coronal hole and coronal dimming fields plays an important role during this
merging event, as the footpoint switching resulting from the reconnection
allows the coronal dimming to intrude onto the boundary of the southern polar
coronal hole.
