Ngampoopun, Nawin;
(2025)
Investigating the Evolution of Solar Open Magnetic Field Regions.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
A significant portion of the Sun's magnetic field is "open"; a pathway for plasma to escape from the atmosphere into the heliosphere as the solar wind. In this thesis, I investigate the evolution and dynamics of open magnetic field regions and their boundaries, as well as the solar wind streams that emanate from them. First, the interaction between a large equatorial hole and the surrounding environment is tracked continuously for several days using observations from the Solar Dynamics Observatory. The plasma properties and spatial complexity of the coronal hole boundary are determined quantitatively through differential emission measure and correlation dimension analyses. I find that each section of the boundary has different plasma properties and structure, likely due to different surrounding magnetic field environments. Next, a unique observation of the merging of the southern polar coronal hole with an adjacent coronal dimming is investigated. Utilising multi-spacecraft observations, I provide the first spectroscopic analysis of the merging of two open-field structures. The coronal dimming appears to be indistinguishable from the coronal hole after the merging occurs, and component reconnection is proposed to play an important role during the merging process. Finally, solar wind outflows originating from a small coronal hole and an open-field corridor are observed at two different heights in the solar atmosphere by combining coronagraph and spectroscopic observations from Solar Orbiter and Hinode. Although the plasma properties of the two source regions are relatively similar in the low corona, they become noticeably different in the middle corona. These pronounced differences may arise from the dynamic nature of the low-middle corona, as is evident by the evolution of fine-scale structures in open-field regions driven by magnetic reconnection.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Investigating the Evolution of Solar Open Magnetic Field Regions |
| Language: | English |
| Additional information: | Copyright © The Author 2025. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10209366 |
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