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Title: Evolution of bright points, x-ray jets, their physical parameters and magnetic field in and around coronal holes
Author: Huang , Zhengua
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2013
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Coronal holes exhibit a more rigid rotation with respect to the typical differential rotation at photospheric levels, and thus interchange magnetic reconnection happens at coronal hole boundaries. Transient brightenings (i.e. coronal bright points and X-ray jets) in and around coronal holes have been found to be signatures of this process. However, evolution of these events, their physical parameters and magnetic field have not been fully understood. In this thesis, we studied the evolution of tens of brightening events, their physical parameters and magnetic field in and around coronal holes by combining observations from spectrometers (SOHO/SUMER and Hinode/ EIS), imager (HinodeIXR1) and polarimager (H inode/S01). We found: the events in coronal holes and their boundaries were very dynamic, producing high-density outflows at high speeds; most of these events represented X-ray jets from coronal bright points pre-existing or newly emerging at X-ray temperatures; the quiet Sun transient brightenings did not produce jet-like phenomena; all brightening events in both coronal holes and quiet-Sun regions were associated with bipolar regions and were caused by magnetic flux emergence followed by cancellation with the preexisting and/or newly emerging magnetic flux; the emission variations seen in the Xray bright points and jets were associated with recurring magnetic cancellation in the footpoints; the magnetic flux cancellation rate during the jet was much higher than that in bright points; the coronal bright point consists of multiple brightening cores as seen in the transition region, which was then suggested from SOT magnetograms as multiple loops. We concluded that the transient brightening events are indeed related to the dynamics of the coronal hole boundaries. They correspond to an energy transporting process in the solar atmosphere, and are important in understanding the coronal heating problem. When occurring in and around coronal holes, they are possible the sources of the slow solar wind.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available