Shear and vortex motions in a forming sunspot - Twist relaxation in magnetic flux ropes
Shear and vortex motions in a forming sunspot - Twist relaxation in magnetic flux ropes
复制标题
正在形成的太阳黑子中的剪切和涡旋运动 - 磁通绳中的扭转弛豫
DOI：
10.1051/0004-6361/201118005
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发表时间：
2012
影响因子：
6.5
通讯作者：
R. Schlichenmaier
中科院分区：
文献类型：
--
作者：
N. Bello Gonzalez;F. Kneer;R. Schlichenmaier
目的测量正在形成的太阳黑子中精细结构的自行运动，以推断光球亚水平通量涌现的动力学信息。方法2009年7月，利用位于泰德/特内里费岛天文台的真空塔望远镜对NOAA11024活动区进行了数天的观测。在这里，我们集中在7月4日拍摄的两个小时的序列，当时领先的地点处于其演化的早期阶段。利用FeIλ6173的CaiiK图像和偏振数据进行散斑重建，我们可以研究银幕精细结构的自然运动。结果我们发现了三个突出的特征：(1)光桥沿其轴线被一条暗道分隔，其两侧呈现相反方向的自行运动，速度为∼100-500ms−1。(2)在一个本影区域，本影圆点勾勒出一个速度高达550ms−1的旋涡，其运动方向与光桥中不同。(3)在半影形成之前，在本影的一个边缘，磁场的精细结构以250-300ms−1的典型速度水平移动。结论我们报道了形成黑子中的剪切和涡旋运动，并将其解释为磁通量绳中扭转弛豫的示踪物。我们认为，形成的太阳黑子包含分离的磁通绳，它们出现在表面，扭曲程度不同。当它们合并形成太阳黑子时，它们会解旋，从而产生观测到的切变和涡旋运动。
AimsWe measure proper motions of fine structures in a forming sunspot to infer information about the dynamics of flux emergence at the sub-photospheric level.MethodsThe active region NOAA11024 was observed with the Vacuum Tower Telescope at Observatorio del Teide/Tenerife over several days in July 2009. Here, we concentrate on a two-hour sequence taken on July 4, when the leading spot was at an early stage of its evolution. Speckle reconstructions from Ca iiK images and polarimetric data in Fe i λ6173 allow us to study proper motions of umbral fine structures.ResultsWe detect three prominent features: (1) A light bridge, divided by a dark lane along its axis, shows proper motions in opposing directions on its sides, with velocities of ∼100–500 ms−1. The flows are seen in both the Ca iiK and the broadband time sequences. (2) Umbral dots in one umbral region outline a vortex with speeds of up to 550 ms−1. The direction of the motion of the umbral dots is different from that in the light bridge. (3) At one rim of the umbra, the fine structure of the magnetic field moves horizontally with typical velocities of 250–300 ms−1, prior to the formation of the penumbra.ConclusionsWe report on shear and vortex motions in a forming sunspot and interpret them as tracers of twist relaxation in magnetic flux ropes. We suggest that the forming sunspot contains detached magnetic flux ropes that emerge at the surface with different amounts of twist. As they merge to form a sunspot, they untwist giving rise to the observed shear and vortex motions.