1. Observations and NLFFF Modeling of AR 10953 Yingna Su 1,2 Collaborators: A. A. Van Ballegooijen 1, E. E. Deluca 1, Leon Golub 1 P. Grigis 1, B. Lites 3, G. L. Huang 2 1. Harvard-Smithsonian Center for Astrophysics, USA 1. Harvard-Smithsonian Center for Astrophysics, USA 2. Purple Mountain Observatory, China 2. Purple Mountain Observatory, China 3. High Altitude Observatory, USA 3. High Altitude Observatory, USA AGU/SPD, Fort Lauderdale, 05/29/2008

2. Outline  Background  NLFFF Modeling of AR 10953 Flux Rope Insertion Method Data: SOHO/MDI, Hinode/SOT, KSO/H-alpha, Hinode/XRT  Observations of a C8.5 Flare in AR 10953 Data: Hinode/XRT, TRACE, RHESSI, MLSO/H-alpha  Interpretations and Conclusions

3. Background  Existing methods for reconstructing NLFFFs (non-linear force free fields) Most methods : extrapolating photospheric vector fields to the corona (Schijver et al. 2006). The method we adopted : “flux rope insertion method” (van Ballegooijen 2004; Bobra etal. 2008) which requires line of sight magnetograms. This method was tested by Bobra et al. 2008, and the model was constrained by TRACE observations.  What is the 3D pre-flare magnetic configuration? Where and how is the flare initiated?  In this work, we construct NLFFF models for the pre-flare state, and the model is constrained by multiple non-potential X-ray loop observed by XRT.

4. Flux Rope Insertion Method PF modelInsert Flux RopeNLFFF Model MDI+SOT/SP 2007-May-02 17:30 UT KSO/H-alpha 2007-May-02 11:31 UT2007-May-02 14:59 UT XRT MDI+SOT/SP Magneto Friction Van Ballegooijen 2004; Bobra et al. 2008

5. Model Restriction: X-ray Loops Best fit model field lines for four non-potential X-ray loops Model Free Parameters: Axial flux and Poloidal flux of the flux rope

6. Model Axial Flux (Mx) Loop 1 14:49:09 UT Loop 2 15:17:04 UT Loop 3 22:58:20 UT Loop 4 18:17:27 UT NLFFF 5e200.00170.00350.00390.0067Y 7e200.00200.00220.00180.0047Y 9e200.00250.00240.00130.0034Y 12e200.00310.00260.00180.0020Y 15e200.00560.00310.00240.0012? Table 1 The Average Deviations of the best-fit model field lines from the observed X-ray loops for various models with fixed Poloidal Flux (1e10 Mx/cm). Calculation Solution Set  Best Fit Model: Axial Flux=7e20±2e20 Mx, upper limit ~ 15e20Mx Poloidal Flux ~ 1e9 to 1e11 Mx/cm  Loop 4 may be in a non-stable state.

7. Vector Magnetogram: Obs. Versus Mod. Best Fit Model: Axial Flux=7e20 and 9e20 Mx Blue Vector: Observation Black Vector: Model

8. Vector Magnetogram: Obs. Versus Mod. Best Fit Model: Axial Flux=7e20 and 9e20 Mx Blue Vector: Observation Black Vector: Model worst fit good fit worse fit

9. Observations of C8.5 Flare MLSO/H-alpha TRACE/171 XRT/Ti_poly  Filament Activation (23:30 UT) associated with the flare was seen in H-alpha and EUV, not X-ray.  Two-ribbon flare: unsheared-sheared-unsheared.

10. Light Curves of C8.5 Flare EUV flare starts about 20 minutes later than the X-ray (XRT and RHESSI) flare, Why?

11. Pre-EUV X-ray brightenings: Unsheared XRT RHESSI XRT TRACE RHESSI Spectral fitting suggests that the pre-EUV flare X-ray sources are mainly caused by thermal bremsstrahlung emission.

12. XRT 2005-May-02 23:09:24 UT Where the Flare Starts? ----- Modeling Result The flare starts from outside boundary of the current layer (on the top of the flux rope), NOT within or under the flux rope. Loop 5

13. Interpretations and Conclusions (I)  For AR 10953, the axial flux of the model flux rope is well constrained (7e20±2e20 Mx) by the observed X-ray loops, while the poloidal flux has a larger range (1e9-1e11 Mx/cm). This result is consistent with the comparisons of observed and modeled photospheric vector magnetograms.  The axial flux in the flux rope is far away from the upper limit for eruption, which is consistent with the fact that no successful filament eruption occurred in this active region.

14. Interpretations and Conclusions (II)  The X-ray brightenings appears about 14 minutes earlier than the EUV flare associated with a filament activation, which may be caused by the localized coronal heating.  Unlike the strong-weak shear motion in most of the two-ribbon flares included in Su et al. 2007, this flare starts from unsheared brightenings, which may be explained as that the flare starts from the outside boundary of the current layer.

15. Thank you for your attention !