The structure and evolution of a sigmoidal active region

Solar coronal sigmoidal active regions have been shown to be precursors to some coronal mass ejections. Sigmoids, or S-shaped structures, may be indicators of twisted or helical magnetic structures, having an increased likelihood of eruption. We present here an analysis of a sigmoidal region's...

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Guardado en:
Detalles Bibliográficos
Publicado: 2002
Materias:
MHD
Sun: activity
Sun: magnetic fields
Acceso en línea:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0004637X_v574_n2I_p1021_Gibson
http://hdl.handle.net/20.500.12110/paper_0004637X_v574_n2I_p1021_Gibson
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
id paper:paper_0004637X_v574_n2I_p1021_Gibson
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spelling paper:paper_0004637X_v574_n2I_p1021_Gibson2025-07-30T17:12:10Z The structure and evolution of a sigmoidal active region MHD Sun: activity Sun: magnetic fields Solar coronal sigmoidal active regions have been shown to be precursors to some coronal mass ejections. Sigmoids, or S-shaped structures, may be indicators of twisted or helical magnetic structures, having an increased likelihood of eruption. We present here an analysis of a sigmoidal region's three-dimensional structure and how it evolves in relation to its eruptive dynamics. We use data taken during a recent study of a sigmoidal active region passing across the solar disk (an element of the third Whole Sun Month campaign). While S-shaped structures are generally observed in soft X-ray (SXR) emission, the observations that we present demonstrate their visibility at a range of wavelengths including those showing an associated sigmoidal filament. We examine the relationship between the S-shaped structures seen in SXR and those seen in cooler lines in order to probe the sigmoidal region's three-dimensional density and temperature structure. We also consider magnetic field observations and extrapolations in relation to these coronal structures. We present an interpretation of the disk passage of the sigmoidal region, in terms of a twisted magnetic flux rope that emerges into and equilibrates with overlying coronal magnetic field structures, which explains many of the key observed aspects of the region's structure and evolution. In particular, the evolving flux rope interpretation provides insight into why and how the region moves between active and quiescent phases, how the region's sigmoidicity is maintained during its evolution, and under what circumstances sigmoidal structures are apparent at a range of wavelengths. 2002 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0004637X_v574_n2I_p1021_Gibson http://hdl.handle.net/20.500.12110/paper_0004637X_v574_n2I_p1021_Gibson
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic MHD
Sun: activity
Sun: magnetic fields
spellingShingle MHD
Sun: activity
Sun: magnetic fields
The structure and evolution of a sigmoidal active region
topic_facet MHD
Sun: activity
Sun: magnetic fields
description Solar coronal sigmoidal active regions have been shown to be precursors to some coronal mass ejections. Sigmoids, or S-shaped structures, may be indicators of twisted or helical magnetic structures, having an increased likelihood of eruption. We present here an analysis of a sigmoidal region's three-dimensional structure and how it evolves in relation to its eruptive dynamics. We use data taken during a recent study of a sigmoidal active region passing across the solar disk (an element of the third Whole Sun Month campaign). While S-shaped structures are generally observed in soft X-ray (SXR) emission, the observations that we present demonstrate their visibility at a range of wavelengths including those showing an associated sigmoidal filament. We examine the relationship between the S-shaped structures seen in SXR and those seen in cooler lines in order to probe the sigmoidal region's three-dimensional density and temperature structure. We also consider magnetic field observations and extrapolations in relation to these coronal structures. We present an interpretation of the disk passage of the sigmoidal region, in terms of a twisted magnetic flux rope that emerges into and equilibrates with overlying coronal magnetic field structures, which explains many of the key observed aspects of the region's structure and evolution. In particular, the evolving flux rope interpretation provides insight into why and how the region moves between active and quiescent phases, how the region's sigmoidicity is maintained during its evolution, and under what circumstances sigmoidal structures are apparent at a range of wavelengths.
title The structure and evolution of a sigmoidal active region
title_short The structure and evolution of a sigmoidal active region
title_full The structure and evolution of a sigmoidal active region
title_fullStr The structure and evolution of a sigmoidal active region
title_full_unstemmed The structure and evolution of a sigmoidal active region
title_sort structure and evolution of a sigmoidal active region
publishDate 2002
url https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0004637X_v574_n2I_p1021_Gibson
http://hdl.handle.net/20.500.12110/paper_0004637X_v574_n2I_p1021_Gibson
_version_ 1840323250533433344

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