1. Structure and Flow Field of Sunspot
Na Deng

2. Structure of Sunspot Magnetic Field Magnetic Field Magnetic nature
Central dark umbra, vertical field
Surrounding penumbra, more inclined field
Wilson depression
Lower temperature because strong magnetic field prevents heat flux from deeper layer.
Umbra
Umbra
Penumbra

3. Sunspot Fine Structure
Umbral dots
Penumbral grains
Penumbral filaments
Penumbral dark cores
Light bridge
Super penumbra
Parker (1979)
(Schlichenmaier et al. 1998)

4. Sunspot Fine Structure
Umbral dots
Penumbral grains
Penumbral filaments
Penumbral dark cores
Light bridge
Super penumbra

5. Sunspot Fine Structure
Umbral dots
Penumbral grains
Penumbral filaments
Penumbral dark cores
Light bridge
Super penumbra

6. Sunspot Fine Structure
Umbral dots
Penumbral grains
Penumbral filaments
Penumbral dark cores
Light bridge
Super penumbra

7. Flow Field of Sunspot Dynamics of umbral dots and penumbral grains
Evershed flow
Inverse Evershed flow
Moat flow
Moving magnetic features (MMFs)
Denker et al. (2007)

8. Motivation Important Questions
Sunspots are the host of most solar eruptions because of their strong and complex magnetic nature. They indicate the magnetic activity level of the Sun. Detailed study of sunspot not only are necessary for understanding the basic principle of magnetic field evolution in the Sun, but also may provide clues on how the energy build up and transport for solar eruptions.
Important Questions
What causes the rapid formation of penumbra?
What drives the flow which produces the Evershed effect?
How do sunspots decay?
What is the three-dimensional flow structure around sunspot?
Is the surrounding flow field responsible for or the result of sunspot evolution?
Do flaring active regions always show complicated flows? Does a correlation between shear flows and major flares exist?

9. Data and Methods Used to Study Sunspot
Morphology
High spatial and temporal resolution. Dynamics. Evolution.
Ground: Large aperture telescope, such as NST. AO, Speckle
Space: seeing free, uninterrupted, long-term
Local correlation tracking/feature tracking for measuring proper motion
Spectroscopy
High spectral resolution
Line profile analysis. Determine line shift for Dopplergram. Bisector. Line asymmetry. Height dependence of Doppler velocity.
Measure magnetic field. Zeeman-Hanle effect. Stokes profiles.
Statistical Study
To find a common/mean law.
Detailed Case Study
Offer detailed insight into the individual processes.

10. Rapid Sunspot Structure Change AFTER Flares
TRACE White-Light
MDI Magnetogram

11. Shear Flows along Magnetic Inversion Lines

12. Evolution of Structure and Flow Field Involved in Sunspot Decay
Basic flow pattern remains during the decay phase, even after penumbra totally disappear.
Moat flow survives for the residual pore.
Large-Scale Convective Cells
Bovelet & Wiehr (2003)

13. Moat Flow Around Sunspot and Pore
Vargas Domínguez 2007 ApJL:
Moat flow is coupled with radial-directed penumbrae. There is no moat flow around pore.

14. Perspective Hinode SOT: 0.2~0.3”
NST VIM and IRIM in conjunction with AO and Speckle: < 0.1”, can resolve fundamental structure in sunspots.
High resolution observation of flaring sunspots.
Study innate and residual pores to provide clues on how the penumbra forms and decays.