The Structure and Evolution of a Sigmoidal Active Region

• Autores: Gibson, S. E.; Fletcher, L.; Del Zanna, G.; Pike, C. D.; Mason, H. E.; Mandrini, Cristina Hemilse; Démoulin, Pascal; Gilbert, H.; Burkepile, J.; Holzer,T.; Alexander, D.; Liu, Y.; Nitta, N.; Qiu, J.; Schmieder, B.; Thompson, B.
• Año de publicación: 2002
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Magnetohydrodynamics; Solar Activity; Solar Magnetic Fields
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

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.
Fil: Gibson, S. E.. National Center for Atmospheric Research; Estados Unidos
Fil: Fletcher, L.. University of Glasgow; Reino Unido
Fil: Del Zanna, G.. University of Cambridge; Reino Unido
Fil: Pike, C. D.. Rutherford Appleton Laboratory; Reino Unido
Fil: Mason, H. E.. University of Cambridge; Reino Unido
Fil: Mandrini, Cristina Hemilse. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina
Fil: Démoulin, Pascal. Centre National de la Recherche Scientifique. Observatoire de Paris; Francia
Fil: Gilbert, H.. National Center for Atmospheric Research; Estados Unidos
Fil: Burkepile, J.. National Center for Atmospheric Research; Estados Unidos
Fil: Holzer,T.. National Center for Atmospheric Research; Estados Unidos
Fil: Alexander, D.. Lockheed-Martin Solar and Astrophysics Laboratory; Estados Unidos
Fil: Liu, Y.. University of Stanford; Estados Unidos
Fil: Nitta, N.. Lockheed-Martin Solar and Astrophysics Laboratory; Estados Unidos
Fil: Qiu, J.. New Jersey Institute Of Technology; Estados Unidos
Fil: Schmieder, B.. Centre National de la Recherche Scientifique. Observatoire de Paris; Francia
Fil: Thompson, B.. National Aeronautics and Space Administration. Goddart Institute for Space Studies; Estados Unidos