1. Changyi Tan et al. NJIT, April 2008 Evolution of Evershed and Shear Flows Associated with the X3.4 Flare of 2006 December 13 Evolution of Evershed and Shear Flows Associated with the X3.4 Flare of 2006 December 13

2. April-1-2008 2 Motivation NJIT solar group has reported the rapid penumbra decays are associated with the X- class flares (Spirock et al. 2002; Wang et al. 2002a,b,2004; Liu et al. 2005; Deng et al. 2005). NJIT solar group has reported the rapid penumbra decays are associated with the X- class flares (Spirock et al. 2002; Wang et al. 2002a,b,2004; Liu et al. 2005; Deng et al. 2005). We rise two questions: We rise two questions: Is Evershed flow change accompanying with flare and the penumbra decay? Is Evershed flow change accompanying with flare and the penumbra decay? Magnetic shear angle could be a proxy of magnetic nonpotentiality (Zhang 2001; Falconer 2001; Wang et al. 2006). Can we expect a decrease in shear flow after the flare? Magnetic shear angle could be a proxy of magnetic nonpotentiality (Zhang 2001; Falconer 2001; Wang et al. 2006). Can we expect a decrease in shear flow after the flare?

3. April-1-2008 3 Data Set Hinode SOT G-band images are from Broadband Filter Imager (BFI), 0.109”, 2 minutes cadence. Stokes V images are from Narrowband Filter Imager (NFI), 0.16”, 2 minutes cadence. From 01:00:32 to 04:36:37 UT Dec. 13, 2006

4. April-1-2008 4 Method Local correlation tracking (LCT). Local correlation tracking (LCT). Running calculation technique, time window is 62 minutes. Running calculation technique, time window is 62 minutes. Correction of the pixel size foreshortening. Correction of the pixel size foreshortening. Shear flow is estimated by the relative motions between two magnetic polarities near the magnetic neutral line. Shear flow is estimated by the relative motions between two magnetic polarities near the magnetic neutral line.

5. April-1-2008 5 Penumbra Decay

6. April-1-2008 6 Penumbra Decay

7. April-1-2008 7

8. 8 LCT applied LCT applied on G-Band data to get the Evershed flows in the penumbra decay areas. on G-Band data to get the Evershed flows in the penumbra decay areas.

9. April-1-2008 9 LCT applied LCT applied on Stokes V data to get the shear flows. on Stokes V data to get the shear flows.

10. April-1-2008 10 Results 1 2

11. April-1-2008 11 Results 3 4

12. April-1-2008 12 Results As a comparison, area 5 is a relatively penumbra constant area. As a comparison, area 5 is a relatively penumbra constant area. 5

13. April-1-2008 13 Results 6

14. April-1-2008 14 Conclusions The penumbra decay appeared obviously in this active region associated with the X3.4 flare. The penumbra decay appeared obviously in this active region associated with the X3.4 flare. The mean magnitude of the horizontal Evershed flows inside the penumbra decay areas varied from 0.4 to 1 km/s temporally and spatially. The mean magnitude of the horizontal Evershed flows inside the penumbra decay areas varied from 0.4 to 1 km/s temporally and spatially. The attenuation of Evershed flows in all the four penumbra decay areas happened during the flare. The attenuation of Evershed flows in all the four penumbra decay areas happened during the flare. The Evershed flows decreased before the flare eruption in two of the four strong penumbra decay areas. The Evershed flows decreased before the flare eruption in two of the four strong penumbra decay areas. The mean shear flows along the magnetic neutral of this delta sunspot started to decrease before the flare and continued to decrease for another hour after the flare. The magnitude of this flow apparently dropped from 0.2 to 0.05 km/s. The mean shear flows along the magnetic neutral of this delta sunspot started to decrease before the flare and continued to decrease for another hour after the flare. The magnitude of this flow apparently dropped from 0.2 to 0.05 km/s.

15. April-1-2008 15 Discussions Open questions: Why do the Evershed flows cease before the flare? Why do the Evershed flows cease before the flare? When do the flow decays exactly start? Can we propose the flow decay as one of flare precursors? When do the flow decays exactly start? Can we propose the flow decay as one of flare precursors?

16. April-1-2008 16 Thank You