A quantitative study relating observed shear in photospheric magnetic fields to repeated flaring
A quantitative study relating observed shear in photospheric magnetic fields to repeated flaring
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DOI：
10.1007/bf00213618
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发表时间：
1984-03
期刊：
影响因子：
2.8
通讯作者：
M. Hagyard;J. B. Smith;D. Teuber;E. West
中科院分区：
文献类型：
--
作者：
M. Hagyard;J. B. Smith;D. Teuber;E. West
在本文中，我们提出了在耀斑活动时期一个活跃区域沿中性线的磁场剪切的定量评价。我们将切变定义为光球中符合观测视距场边界条件的势磁场与观测磁场之间的角差。对于所研究的活动区域，这种角差（剪切）沿着中性线是不均匀的，最大值出现在重复耀斑发作的位置。我们认为，持续的磁演化导致磁场的最大剪切超过剪切的临界值，导致最大剪切位置周围的耀斑。显然，耀斑位置的场必须松弛到略低于临界值的剪切状态（但仍远离势），随后的演化使场返回到临界阈值。我们得出这个结论是因为几个耀斑发生在最大光球剪切的位置，这些位置持续存在。
In this paper we present a quantitative evaluation of the shear in the magnetic field along the neutral line in an active region during an epoch of flare activity. We define shear as the angular differencein the photospherebetween the potential magnetic field, which fits the boundary conditions imposed by the observed line-of-sight field, and the observed magnetic field. For the active region studied, this angular difference (shear) is non-uniform along the neutral line with maxima occurring at the locations of repeated flare onsets. We suggest that continued magnetic evolution causes the field's maximum shear to exceed a critical value of shear, resulting in a flare around the site of maximum shear. Evidently, the field at the site of the flare must relax to a state of shear somewhat below the critical value (but still far from potential), with subsequent evolution returning the field to the critical threshold. We draw this inference because several flares occurred at sites of maximum photospheric shear which were persistent in location.