1. Contraction of flaring loops — the evidence of magnetic reconnection in sheared core fields Haisheng Ji Purple Mountain Observatory Nanjing, 210008, China jihs@pmo.ac.cn

2. What is the Contraction of flaring loops? That is, during the rising phase of solar flares, hard X-ray (HXR) loop-top sources or radio/extreme-ultraviolet (EUV) flaring loops have a descending motion and, at the same time, Hα ribbons or HXR footpoints (FPs) are converging. The usual expansion motion (upward motion + separation motion) of flaring loops occurs only after the contraction. Unshearing occurs during the contraction as well as the expansion motion.

3. Dynamic flaring loops — A Summary from our observations

5. 中国古代天文学家对太阳黑子的描述，大体可分为三大类： 第一类，圆形：如钱、如桃、如李、如栗、如环。 第二类，椭圆形：如鸡卵、鸭卵、鹅卵、爪、枣。 第三类，不规则形：如立人、如踆乌、如飞鹊、如飞燕。

6. 《淮南子 精神训》载： “ 日中有踆乌，而月中有蟾蜍。 ” 东 汉高诱注云： “ 踆，犹 ‘ 蹲 ’ 也，谓三足乌。 ” 晋代学者郭璞 （ 276 ～ 324 ）也有注释说 “ 中有三足乌 ” 。

7. Events showing the contraction The M1.2 flare of 2002-04-15 (Sui & Holman 2003) The M2.1 flare of 2002-09-09 (Ji et al. 2004) The X3.1 flare of 2002-08-24 (Li & Gan 2005) The X3.9 flare of 2003-11-03 (Veronig et al. 2006) The M1.2 flare of 2004-11-01 (Ji et al. 2006) The M6.8 flare of 2003-06-13 (Ji, Huang, & Wang 2007) The M5.7 flare of 2002-03-14 (Zhou, Ji & Huang 2006) The X10 flare of 2003-10-29 (Zhou, Ji & Huang 2006; Ji et al. 2008)

8.  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 (Sui and Holman 2003) the first SMESE workshop 10-12 March 2008, Paris

9. The X3.1 flare of 2002-08-24 (Li and Gan 2005) the first SMESE workshop 10-12 March 2008, Paris

10. The M3.9 flare of 2003-11-03 (Veronig et al. 2006) the first SMESE workshop 10-12 March 2008, Paris

11. The M2.1 flare of 2002-09-09 (Ji et al. 2004) Red: 6-12keV Blue: 12-25kev 25-50 keV 25 km/s 17:41 UT 17:46UT

12. The M1.2 flare of 2004-11-01: (Ji et al. 2006) 03:18:44 – 03:18:56 03:19:08 – 03:19:20 Solid: 25-60 keV Dashed: 6-10 keV the first SMESE workshop 10-12 March 2008, Paris

13. The M6.8 flare of 2003-06-17 (Ji et al. 2007)

14. The flare of 2002-03-14 (Zhou et al. 2007) Background: TRACE 171 A Contours: HXR 30-60 keV the first SMESE workshop 10-12 March 2008, Paris

15. White-light flare (Xu et al. 2004) Penumbral decay and rapid magnetic changes (Wang et al. 2004) Gamma-ray (Hurford et al. 2006) Large scale disturbance (Liu et al. 2006; Balasubramaniam, Pevtsov \& Neidig 2007) Shear flows (Deng et al. 2006) Magnetic unshearing after flare (Wang et al. ) Significant helicity drop after flare (Liu et al. 2007) Significant geophysical effect (Kwabara et al. 2004) Contraction-to-expansion (Zhou et al. 2007) The X10 flare of 2003-10-29 (Ji et al. 2008)

16. 10-25 keV35-50 keV The X10 flare of 2003-10-29 (Ji et al. 2008) the first SMESE workshop 10-12 March 2008, Paris

17. The X10 flare of 2003-10-29 Sigmoid arcade the first SMESE workshop 10-12 March 2008, Paris

18. The X10 flare of 2003-10-29 (Ji et al. 2008) the first SMESE workshop 10-12 March 2008, Paris

19. Sigmoid phase Arcade phase The X10 flare of 2003-10-29 (Ji et al. 2008)

20. The X10 flare of 2003-10-29 (Ji et al. 2008) the first SMESE workshop 10-12 March 2008, Paris

21. Contractionexpansion The X10 flare of 2003-10-29 (Ji et al. 2008) the first SMESE workshop 10-12 March 2008, Paris

22. Sigmoidal structure first ever seen in HXR Magnetic reconnection inside the sigmoid Sigmoid  arcade Contraction  expansion Unshearing throughout the flare Rapid unshearing during the ‘sigmoid’ period The X10 flare of 2003-10-29 (Ji et al. 2008) the first SMESE workshop 10-12 March 2008, Paris

23. the first SMESE workshop 10-12 March 2008, Paris

24. Contraction of flaring loops ☆ inward motion of conjugate flaring kernels ☆ shrinkage of flaring loops (radio, EUV) ☆ descending of HXR looptop sources Expansion of flaring loops ☆ outward motion of conjugate flare ribbons ☆ expansion of flare loops (radio, EUV) ☆ upward motion of HXR looptop sources the first SMESE workshop 10-12 March 2008, Paris

25. dynamic flare loops A B CD E F G the first SMESE workshop 10-12 March 2008, Paris

26. dynamic flare loops the first SMESE workshop 10-12 March 2008, Paris

27. 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 the first SMESE workshop 10-12 March 2008, Paris

28. Mapping effect from the Photosphere Modifying effect caused by Our interpretation (Ji et al. 2007) the first SMESE workshop 10-12 March 2008, Paris

29. Our interpretation (Ji et al. 2007) Contraction is the signature of magnetic energy dissipation in highly sheared magnetic field Energy dissipation the first SMESE workshop 10-12 March 2008, Paris

30. The implication for the relationship of flares and CMEs sigmoidal phasearcade phase contraction expansion + + CMEs the first SMESE workshop 10-12 March 2008, Paris

31. THANK YOU! the first SMESE workshop 10-12 March 2008, Paris