1. Multiheight Analysis of Asymmetric Stokes Profiles in a Solar Active Region Na Deng Post-Doctoral Researcher at California State University Northridge (CSUN)

2. Observation NSO/HAO Advanced Stokes Polarimeter (ASP) FeI 630.15 & 630.25 Line Pair Photosphere MgI b2 517.27 Line Low Chromosphere

3. FeI Continuum ImageMimic Magnetogram Active Region NOAA 9661 9661 2001 Oct 17 NOAA 9661 Near Disc Center

4. Intensity + Magnetic Polarity

5. Stokes Asymmetries  Large gradient of magnetic field along LOS  Large gradient of velocity field along LOS  Inhomogeneous atmosphere that contains two or more magnetic components  Spatially unresolved flows, i.e., superposition of components with large Doppler velocity relative to each other.  Spatially unresolved mixed polarities  Spreading of Stokes signals due to seeing and diffraction Origin of Stokes Asymmetries

6. Stokes Asymmetry Images 50 km 200 km 600 km Photosphere Photosphere Low Chromosphere FeI 630.25 FeI 630.15 Mg b 517.27

7. 630.25 630.15 517.27 Extremely Strong Down Flows along Neutral Line Line Center Shift of Stokes ‒ I 630.25 630.15 517.27 Zero-Crossing Shift of Stokes ‒ V

8. Intensity ImageMagnetogram Dopplergram (Intensity) + (Dopplergram) MDI high-resolution data reinforce ASP observations. They show at the same locations strong downflows with mean speed of 0.98 km/s and maximum speed of 1.28 km/s. While the limb side Evershed flow of the nearby alpha spot is only about 0.36 km/s. MDI High-Resolution Data on 2001/10/17

9. Horizontal penumbral Evershed flow channels get bended downward when they encounter strong vertical field of another umbra with opposite polarity. Therefore, horizontal Evershed flow becomes downflow at the boundary between outer penumbra of one polarity and umbra of the other polarity. Interpretation

10. Future Work Collaborate with Dr. Thomas Wiegelmann to study 3D evolution of the active region associated with the flare occurred on Oct 19 th. Compare the difference in the extrapolated result between different input boundary conditions: photospheric vector magnetogram and vector magnetogram in low chromosphere. Available Data: Vector magnetograms in both photosphere and low chromosphere On Oct 16, 17, and 19.