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Low coronal signatures of coronal mass ejections: coronal “waves” and dimmings

Attrill, G.D.R.; (2009) Low coronal signatures of coronal mass ejections: coronal “waves” and dimmings. Doctoral thesis, UCL (University College London). Green open access

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[img]MPEG video (Supplementary video from Chapter 6: A movie of contour plots showing the evolution of the dimmings on 6th July 2006)
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[img]MPEG video (Supplementary video from Chapter 6: A movie of contour plots showing the evolution of the dimmings on 13th May 2005)
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[img]MPEG video (Supplementary video from Chapter 6: A movie of contour plots showing the evolution of the dimmings on 12th May 1997)
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[img]MPEG video (Supplementary video from Chapter 5: The shrinking of the dimming regions as seen in the EIT 195 Å movie)
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[img]MPEG video (Supplementary video from Chapter 4: Base different movie for EIT event, 29th April 2006)
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[img]MPEG video (Supplementary video from Chapter 4: EIT 195 on the 29th April 2006)
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[img]MPEG video (Supplementary video from Chapter 4: EIT (not differenced) movie )
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[img]MPEG video (Supplementary video from Chapter 4: Base different movie for EUVI event, 25th January 2007)
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[img]MPEG video (Supplementary video from Chapter 3: EIT 195 Å movie)
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[img]MPEG video (Supplementary video from Chapter 3: Base different movie of TRACE data)
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[img]MPEG video (Supplementary video from Chapter 3: Base different movie of EIT data)
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Abstract

Coronal mass ejections (CMEs) are vast eruptions of magnetised plasma that explode from the solar atmosphere. This thesis focuses on understanding the nascent stages of CMEs, and their magnetic development as they expand into the interplanetary space of our solar system. This is an important part of our effort to understand the space weather environment that we live in, and increasingly interact with through satellite communications technologies. Predominantly through combining extreme ultra-violet imaging and magnetogram data, two low coronal signatures of CMEs, namely coronal waves and dimmings, are studied. A comprehensive list of observational properties of EIT coronal waves is compiled and potential counterparts in radio, H!, soft X-rays and He II wavelengths are also discussed. New observational constraints on EIT coronal waves are presented, most notably diffuse coronal waves are shown to have a magnetic nature. Finding that many observational constraints are not satisfactorily explained by current theories, a new model for understanding the physical nature of diffuse coronal waves is developed. The new model interprets diffuse coronal “wave” bright fronts to be the low coronal magnetic footprint of CMEs. Implications for developing our understanding of how CMEs become large-scale in the low corona are discussed. Application of the model demonstrates how an understanding of the formation of complex global-scale coronal dimmings can be derived. For the first time it is shown that study of the evolution and magnetic nature of coronal dimming regions can be used to probe the post-eruptive evolution of the CME. Finally, a study is presented regarding why and how CME-related dimmings recover, despite the “open” magnetic connectivity of the ejecta to the Sun being maintained as indicated by electron heat flux measurements at 1 AU.

Type:Thesis (Doctoral)
Title:Low coronal signatures of coronal mass ejections: coronal “waves” and dimmings
Open access status:An open access version is available from UCL Discovery
Language:English
UCL classification:UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Space and Climate Physics

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