EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

The Merging of a Coronal Dimming with the Southern Polar Coronal Hole During Solar Orbiter’s First Perihelion

Nawin Ngampoopun1, David Long2,1, Deborah Baker1, Lucie Green1, Stephanie Yardley3,1, Alexander James1,4, and Andy To1
Nawin Ngampoopun et al.
  • 1Mullard Space Science Laboratory, University College London, Dorking, UK
  • 2Astrophysics Research Centre, Queen’s University Belfast, Belfast, UK
  • 3Department of Meteorology, University of Reading, Reading, UK
  • 4European Space Astronomy Centre, European Space Agency, Madrid, Spain

We report a partial filament eruption in the southern solar hemisphere that occurred on 18 March 2022 during the first science perihelion of Solar Orbiter. The filament erupted into a coronal mass ejection (CME), producing coronal dimmings at the footpoints of the erupting structure. The expanding dimming then merged with the adjacent southern polar coronal hole. This merging of two open magnetic structures is observationally rare and poorly understood. 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 instruments onboard the Solar Orbiter and Solar Dynamic Observatory spacecraft. The plasma dynamics are quantified using spectroscopic data obtained from the EUV Imaging Spectrometer onboard Hinode. The preliminary results show that the coronal hole and coronal dimming become indistinguishable from each other after the merging. Several plasma upflow regions were observed throughout the merging event, suggesting the opening of magnetic field lines. The brightening of bright points and coronal jets inside the merged region further imply ongoing reconnection processes. This work also has implications for the formation of coronal hole/open field regions and the origin of solar wind from coronal dimming and coronal hole boundaries.

How to cite: Ngampoopun, N., Long, D., Baker, D., Green, L., Yardley, S., James, A., and To, A.: The Merging of a Coronal Dimming with the Southern Polar Coronal Hole During Solar Orbiter’s First Perihelion, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-8269,, 2023.

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