DocumentCode :
1436762
Title :
Sigmoids as precursors of solar eruptions
Author :
Canfield, Richard C. ; Hudson, Hugh S. ; Pevtsov, Alexei A.
Author_Institution :
Dept. of Phys., Montana State Univ., Bozeman, MT, USA
Volume :
28
Issue :
6
fYear :
2000
fDate :
12/1/2000 12:00:00 AM
Firstpage :
1786
Lastpage :
1794
Abstract :
Coronal mass ejections (CMEs) appear to originate preferentially in regions of the Sun´s corona that are sigmoidal, i.e., have sinuous S or reverse-S shapes. Yohkoh solar X-ray images have been studied before and after a modest number of Earth-directed (halo) CMEs. These images tend to show sigmoidal shapes before the eruptions and arcades, cusps, and transient coronal holes after. Using such structures as proxies, it has been shown that there is a relationship between sigmoidal shape and tendency to erupt. Regions in the Sun´s corona appear sigmoidal because their magnetic fields are twisted. Some of this twist may originate deep inside the Sun. However, it is significantly modulated by the Coriolis force and turbulent convection as this flux buoys up through the Sun´s convection zone. As the result of these phenomena, and perhaps subsequent magnetic reconnection, magnetic flux ropes form. These flux ropes manifest themselves as sigmoids in the corona. Although there are fundamental reasons to expect such flux ropes to be unstable, the physics is not as simple as might first appear, and there exist various explanations for instability. Many gaps need to be filled in before the relationship between sigmoids and CMEs is well enough understood to be a useful predictive tool
Keywords :
X-ray astronomy; solar corona; solar magnetism; solar prominences; 0.12 to 7 nm; CME; S shape; Sun; X-ray image; arcade; coronal mass ejection; cus; magnetic flux rope; magnetic reconnection; precursor; sigmoid; sigmoidal; solar corona; solar eruption; solar magnetism; solar prominence; transient coronal hole; Corona; Helium; Large-scale systems; Magnetic fields; Magnetic flux; Magnetic reconnection; Physics; Shape; Sun; X-ray imaging;
fLanguage :
English
Journal_Title :
Plasma Science, IEEE Transactions on
Publisher :
ieee
ISSN :
0093-3813
Type :
jour
DOI :
10.1109/27.902208
Filename :
902208
Link To Document :
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