The Relationship between Magnetic Gradient and Magnetic Shear in Five Super Active Regions Producing Great Flares

作     者：Hai-Min Wang Hui Song Ju Jing Vasyl Yurchyshyn Yuan-Yong Deng Hong-Qi Zhang David Falconer Jing Li 

作者机构：National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 Big Bear Solar Observatory New Jersey Institute of Technology Big Bear City CA 92314 USA Marshall Space Flight Center SD50 Huntsville AL 35812 USA Institute for Astronomy University of Hawaii 2680 Woodlawn Drive Honolulu HI 96822 USA 

出 版 物：《Chinese Journal of Astronomy and Astrophysics》 (中国天文和天体物理学报（英文版）)

年 卷 期：2006年第6卷第4期

页      面：477-488页

核心收录：

学科分类：07[理学] 070401[理学-天体物理] 0704[理学-天文学] 

基　　金：Supported by the National Natural Science Foundation of China 

主　　题：Sun: activity    Sun: flares    Sun: magnetic fields    Sun: coronal mass ejections (CMEs) 

摘      要：We study the magnetic structure of five well-known active regions that produced great flares （X5 or larger）. The six flares under investigation are the X12 flare on 1991 June 9 in AR 6659, the X5.7 flare on 2000 July 14 in AR 9077, the X5.6 flare on 2001 April 6 in AR 9415, the X5.3 flare on 2001 August 25 in AR 9591, the X17 flare on 2003 October 28 and the X10 flare on 2003 October 29, both in AR 10486. The last five events had corresponding LASCO observations and were all associated with Halo CMEs. We analyzed vector magnetograms from Big Bear Solar Observatory, Huairou Solar Observing Station, Marshall Space Flight Center and Mees Solar Observatory. In particular, we studied the magnetic gradient derived from line-of-sight magnetograms and magnetic shear derived from vector magnetograms, and found an apparent correlation between these two parameters at a level of about 90%. We found that the magnetic gradient could be a better proxy than the shear for predicting where a major flare might occur： all six flares occurred in neutral lines with maximum gradient. The mean gradient of the flaring neutral lines ranges from 0.14 to 0.50 G km^-1, 2.3 to 8 times the average value for all the neutral lines in the active regions. If we use magnetic shear as the proxy, the flaring neutral line in at least one, possibly two, of the six events would be mis-identified.