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

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

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).

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

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

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.

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

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