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Exploring the dynamics of flux-emergence in magnetically-complex solar active regions

Exploring the dynamics of flux-emergence in magnetically-complex solar active regions

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Exploring the dynamics of flux-emergence in magnetically-complex solar active regions

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  1. Exploring the dynamics of flux-emergence in magnetically-complex solar active regions David Alexander and Lirong Tian Rice University David Alexander Rice University

  2. Twist and writhe in d-configuration active regions Systematic tilt ≡ writhe abest ≡ twist Tian et al., Sol. Phys., 229, 63, 2005a David Alexander Rice University

  3. Twist and writhe in d-configuration active regions 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 d 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 d ARs produce more large flares (but not exclusively). 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 d-configurations without kinking Observations also ‘require’ ARs in QII and QIV emerge with high initial twist Tian et al., Sol. Phys., 229, 63, 2005a David Alexander Rice University

  4. Long-term evolution of active regions: role of kink instability Expect left-handed writhe in South Tian et al., Sol. Phys., 229, 237, 2005b David Alexander Rice University

  5. Long-term evolution of active regions: role of kink instability Clockwise rotating filaments Non-Hale region Tian et al., Sol. Phys., 229, 237, 2005b David Alexander Rice University

  6. Long-term evolution of active regions: role of kink instability 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. Tian et al., Sol. Phys., 229, 237, 2005b David Alexander Rice University

  7. Bringing 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 – d-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 David Alexander Rice University

  8. Future 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 David Alexander Rice University