Structure and Flow Field of Sunspot Na Deng 2007.11.02

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 http://www.nasa.gov/mission_pages/solar-b/index.html

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

Sunspot Fine Structure Umbral dots Penumbral grains Penumbral filaments Penumbral dark cores Light bridge Super penumbra http://www.solarphysics.kva.se/data1/NatGeo/

Sunspot Fine Structure Umbral dots Penumbral grains Penumbral filaments Penumbral dark cores Light bridge Super penumbra http://www.solarphysics.kva.se/data1/NatGeo/

Sunspot Fine Structure Umbral dots Penumbral grains Penumbral filaments Penumbral dark cores Light bridge Super penumbra http://www.solarphysics.kva.se/data1/NatGeo/

Flow Field of Sunspot Dynamics of umbral dots and penumbral grains Evershed flow Inverse Evershed flow Moat flow Moving magnetic features (MMFs) http://www.nasa.gov/mission_pages/solar-b/index.html Denker et al. (2007)

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?

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.

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

Shear Flows along Magnetic Inversion Lines http://www.nasa.gov/mission_pages/solar-b/index.html

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)

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.

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.