The contracting and unshearing motion of flare loops in the X 7.1 flare on 2005 January 20 during its rising phase  

作　　者：Tuan-Hui Zhou Jun-Feng Wang Dong Li Qi-Wu Song Victor Melnikov Hai-Sheng Ji 

机构地区：[1]Key Laboratory for Dark Matter and Space Science, Purple Mountain Observatory, Chinese Academy of Sciences [2]Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences [3]Purple Mountain Observatory, Chinese Academy of Sciences [4]School of Physics Optoelectronic Engineering, Nanjing University of Information Science and Technology [5]Graduate University of Chinese Academy of Sciences

出　　处：《Research in Astronomy and Astrophysics》2013年第5期526-536,共11页天文和天体物理学研究（英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.10833007,11173062,10921303,11178002,10928307and11111120071);the National Basic Research Program of China(973program,Grant No.2011CB811402);supported by the Chinese Academy of Sciences via a visiting professorship for senior international scientists with grant No.2010t2j36;by the joint RFBR-CNSF(Grant No.11-02-91175);supported by the Open Research Program of the Key Laboratory of Solar Activity ofNational Astronomical Observatories;the Scientific Research Foundation of Nanjing Universityof Information Science and Technology(Grant Nos.S8110136001and N1081005072)

摘　　要：With the aim of studying the relationship between the relative motions of the loop-top （LT） source and footpoints （FPs） during the rising phase of solar flares, we give a detailed analysis of the X7.1 class flare that occurred on 2005 January 20. The flare was clearly observed by RHESSI, showing a distinct X-ray flaring loop with a bright LT source and two well-defined hard X-ray （HXR） FPs. In particular, we correct the projection effect for the positions of the FPs and magnetic polarity inversion line. We find that： （1） The LT source showed an obvious U-shaped trajectory. The source of the higher energy LT shows a faster downward/upward speed. （2） The evolution of FPs was temporally correlated with that of the LT source. The converging/separating motion of FPs corresponds to the downward/upward motion of the LT source. （3） The initial flare shear of this event is found to be nearly 50 degrees, and it has a fluctuating decrease throughout the contraction phase as well as the expansion phase. （4） Four peaks of the time profile of the unshearing rate are found to be temporally correlated with peaks in the HXR emission flux. This flare supports the overall contraction pic- ture of flares： a descending motion of the LT source, in addition to converging and unshearing motion of FPs. All results indicate that the magnetic field was very highly sheared before the onset of the flare.With the aim of studying the relationship between the relative motions of the loop-top （LT） source and footpoints （FPs） during the rising phase of solar flares, we give a detailed analysis of the X7.1 class flare that occurred on 2005 January 20. The flare was clearly observed by RHESSI, showing a distinct X-ray flaring loop with a bright LT source and two well-defined hard X-ray （HXR） FPs. In particular, we correct the projection effect for the positions of the FPs and magnetic polarity inversion line. We find that： （1） The LT source showed an obvious U-shaped trajectory. The source of the higher energy LT shows a faster downward/upward speed. （2） The evolution of FPs was temporally correlated with that of the LT source. The converging/separating motion of FPs corresponds to the downward/upward motion of the LT source. （3） The initial flare shear of this event is found to be nearly 50 degrees, and it has a fluctuating decrease throughout the contraction phase as well as the expansion phase. （4） Four peaks of the time profile of the unshearing rate are found to be temporally correlated with peaks in the HXR emission flux. This flare supports the overall contraction pic- ture of flares： a descending motion of the LT source, in addition to converging and unshearing motion of FPs. All results indicate that the magnetic field was very highly sheared before the onset of the flare.

关 键 词：Sun： activity -- Sun： magnetic fields -- Sun： flares 

分 类 号：P182.52[天文地球—天文学] O316[理学—一般力学与力学基础]