exploring the dynamics of flux-emergence in magnetically-complex solar active regions
DESCRIPTION
Exploring the dynamics of flux-emergence in magnetically-complex solar active regions. David Alexander and Lirong Tian Rice University. Twist and writhe in d -configuration active regions. Systematic tilt ≡ writhe a best ≡ twist. - PowerPoint PPT PresentationTRANSCRIPT
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David Alexander Rice University SHINE 2006
Exploring the dynamics of flux-emergence in Exploring the dynamics of flux-emergence in magnetically-complex solar active regions magnetically-complex solar active regions
David Alexander and Lirong TianRice University
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David Alexander Rice University SHINE 2006
Twist and writhe in Twist and writhe in -configuration -configuration active regionsactive regions
Tian et al., Sol. Phys., 229, 63, 2005a
Systematic tilt ≡ writhebest ≡ twist
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David Alexander Rice University SHINE 2006
Twist and writhe in Twist and writhe in -configuration -configuration active regionsactive regions
Tian et al., Sol. Phys., 229, 63, 2005a
These results support the idea of a kink instability driving the active region evolution:
- writhe and twist have same sign (via helicity conservation) a la models by Linton, Fan and others
Models can also yield -configurations without kinking
Observations also ‘require’ ARs in QII and QIV emerge with high initial twist
Both HNJL and HHR are followed by most active regions with simple bipolar (non-δ) magnetic configuration. These ARs have twist of the opposite sign to the writhe (see quadrant I in Figure 2).
Only about 20% of ARs adhere to both HNJL and HHR
For active regions with complex (δ) magnetic configurations, about 34% violate HNJL, but follow HHR, while 32% follow HNJL, but violate HHR. Of the 104 active regions 65–67% have the same sign of the twist and writhe (see quadrants II and IV in Figure 1).
Non-Hale or non-HHR ARs produce more large flares (but not exclusively).
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David Alexander Rice University SHINE 2006
Long-term evolution of active regions: Long-term evolution of active regions: role of kink instabilityrole of kink instability
Tian et al., Sol. Phys., 229, 237, 2005b
Expect left-handed writhe in South
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David Alexander Rice University SHINE 2006
Long-term evolution of active regions: Long-term evolution of active regions: role of kink instabilityrole of kink instability
Tian et al., Sol. Phys., 229, 237, 2005b
Non-Hale region Clockwise rotating filaments
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David Alexander Rice University SHINE 2006
Long-term evolution of active regions: Long-term evolution of active regions: role of kink instabilityrole of kink instability
Tian et al., Sol. Phys., 229, 237, 2005b
Sunspot-group shows pronounced clockwise rotation:
- 8o-10o per day, 220o-270o per solar rotation
Filaments also show clockwise rotation
Clockwise rotation was long-lasting (four solar rotations)
Positive twist indicates right-handed twist, positive tilts indicates right-handed writhe.
Again, these results support the idea of a kink instability driving the active region evolution.
AR must result from a fluxtube with large positive twist with helicity transfer to writhe generating clockwise rotation.
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David Alexander Rice University SHINE 2006
Bringing it all togetherBringing it all together
Detailed studies of active region magnetic field evolution can
yield insight into the sub-surface dynamics of the parent magnetic fluxtubes
delineate magnetic complexity – -configurations, fragmentation, non-Hale-icity – and provide key to generation of coronal free energy
help determine role of twist and writhe – e.g. sunspot rotation and flux emergence – and role of helicity
provide a link between the dynamics of the solar interior and the driving of eruptive coronal phenomena
The kink instability seems to be an important process in flare/CME productive active regions
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David Alexander Rice University SHINE 2006
Future WorkFuture Work
Incorporate better vector magnetic field data into the analysis (Solar-B)
Apply more realistic velocity/field coupling (inductive equation?)
Combine modeling with observation (HAO/Rice collaboration)
Emergence of asymmetric fluxtubes
Driving of solar eruptive phenomena