1. Relaxation of Sheared Magnetic fields — a Process of Contraction

2. Events List The M1.2 flare of 2002-04-15 (Sui and Holman 2003) The M2.1 flare of 2002-09-09 (Ji, Wang, and Goode et al. 2004) The X3.1 flare of 2002-08-24 (Li and Gan 2005) The X3.9 flare of 2003-11-03 (Veronig, Karlicky, and Vrsnak et al. 2006) The M1.2 flare of 2004-11-01 (Ji, Huang, and Wang et al. 2006) The M6.8 flare of 2003-06-13 (Ji, Huang, and Wang 2007) The X10 flare of 2003-10-29 (Zhou, Ji and Huang 2006) The M5.7 flare of 2002-03-14 (Zhou, Ji and Huang 2006) The M1.0 flare of 2002-07-26 (Ji & Wang 2007)

3. 2002/04/15  in the early phase of the flares, the looptop sources moves down  Velocity ~ tens of kilometers per second 10-25 keV The M1.2 flare of 2002-04-15: Motion of looptop sources

4. The M2.1 flare of 2002-09-09: Motion of looptop sources and flare kernels

5. The X3.1 flare of 2002-08-24: shrinkage of flaring loops

6. The M3.9 flare of 2003-11-03: Motion of looptop sources

7. Flare shear

8. The M1.2 flare of 2004-11-01: Motion of looptop sources and flare kernels – Unshear motion 03:18:44 – 03:18:56 03:19:08 – 03:19:20

9. The M1.2 flare of 2004-11-01: Motion of looptop sources and flare kernels – Unshear motion

10. The M6.8 flare of 2003-06-17: Motion of looptop sources, EUV flaring loops and flare kernels – Unshear motion

11. The M6.8 flare of 2003-06-17: Motion of looptop sources, EUV flaring loops and flare kernels – Unshear motion

12. The M6.8 flare of 2003-06-17: Motion of looptop sources, EUV flaring loops and flare kernels – Unshear motion

13. The flare of 2002-03-14 – unshear motion

15. The flare of 2002-03-14

17. The flare of 2003-10-29

19. Expansion of flaring loops ☆ inward motion of conjugate flaring kernels ☆ shrinkage of flaring loops (radio, EUV) ☆ descending of HXR looptop sources Unshear motion during contraction and expansion! Contraction of flaring loops ☆ outward motion of conjugate flaring kernels ☆ expansion of flaring loops (radio, EUV) ☆ upward motion of HXR looptop sources

20. Interpretation of Loop Contraction 10-25 keV 1. Current sheet formation (Sui & Holman 2003, Sui et al. 2004) 2. Magnetic shrinkage (Acton & Forbes1996, Lin 2004) 3. Collapsing magnetic trap (Veronig et al. 2005) 4. Magnetic Implosion (Hudson 2000) reduced

21. Mapping effect from the Photosphere Modifying effect caused by Our interpretation (ApJ, 2007)

24. Unshear rate and HXR spikes The M1.0 flare of 2002-07-26

25. What I am doing ★ A statistical study using old BBSO H-alpha data to study the contracting motion ★ A statistical study using HXR data to study the contracting motion ★ Analyzing the change of flare shear, and its relationship with magnetic shear using more events. ★ The correlation between the unshear rate with HXR spikes. ★ Verifying the analytical model from existing flare data. ★ ….

26. We can estimate the energy releasing rate of a flare Proportional to the GOES magnitude e.g. estimated by the contraction motion an integral over flaring region

28. The M1.1 flareThe M6.7 flare

29. What is the physical meaning of flare shear? e.g.

30. THANKS!