Relationship between Powerful Flares and Dynamic Evolution of the Magnetic Field at the Solar Surface
Relationship between Powerful Flares and Dynamic Evolution of the Magnetic Field at the Solar Surface
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DOI：
10.1007/s11207-008-9149-0
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发表时间：
2008-03
期刊：
影响因子：
2.8
通讯作者：
Jihong Liu;Yin Zhang;Hongqi Zhang
中科院分区：
文献类型：
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作者：
Jihong Liu;Yin Zhang;Hongqi Zhang
太阳耀斑与太阳表面复杂磁场位形的演化密切相关。磁场的强度和演化速度是研究太阳大气磁场变化的两个重要参数。本文提出了活动区复杂性变化的动态定量描述：E=u×B，其中u为磁力线足点运动速度，B为磁场，E代表速度场和磁场的动态演化，表现了磁足点的扫掠运动，反映了电流的建立过程，并与活动区在光球中的非势能变化有关。它实际上是光球层中的感应电场。它可以推断观测从本地相关跟踪（LCT）技术计算的速度和矢量磁场来自矢量磁图。本文研究了E与四个活动区（NOAA 10720、10486、9077和8100）的十个X级耀斑的关系。结果表明：（1）耀斑核的初始增亮大致位于E强度很高的逆温线附近;（2）在大多数情况下，E及其法向分量（En）的平均密度日均值在耀斑发生后都有所下降，而E的切向分量（Et）的平均密度日均值在耀斑发生前后没有明显的变化;（3）Et的平均密度日平均值总是大于En的平均密度日平均值，这不能由Bn和Bt的平均密度日平均值自然推断出来。
Powerful flares are closely related to the evolution of the complex magnetic field configuration at the solar surface. The strength of the magnetic field and speed of its evolution are two vital parameters in the study of the change of magnetic field in the solar atmosphere. We propose a dynamic and quantitative depiction of the changes in complexity of the active region:E=u×B, whereuis the velocity of the footpoint motion of the magnetic field lines andBis the magnetic field.Erepresents the dynamic evolution of the velocity field and the magnetic field, shows the sweeping motions of magnetic footpoints, exhibits the buildup process of current, and relates to the changes in nonpotentiality of the active region in the photosphere. It is actually the induced electric field in the photosphere. It can be deduced observationally from velocities computed by the local correlation tracking (LCT) technique and vector magnetic fields derived from vector magnetograms. The relationship betweenEand ten X-class flares of four active regions (NOAA 10720, 10486, 9077, and 8100) has been studied. It is found that (1) the initial brightenings of flare kernels are roughly located near the inversion lines where the intensities ofEare very high, (2) the daily averages of the mean densities ofEand its normal component (En) decrease after flares for most cases we studied, whereas those of the tangential component ofE(Et) show no obvious regularities before and after flares, and (3) the daily averages of the mean densities ofEtare always higher than those ofEn, which cannot be naturally deduced by the daily averages of the mean densities ofBnandBt.