Resonant Absorption in Complicated Plasma Configurations: Applications to Multistranded Coronal Loop Oscillations
Resonant Absorption in Complicated Plasma Configurations: Applications to Multistranded Coronal Loop Oscillations
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DOI：
10.1086/586733
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发表时间：
2008-02
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影响因子：
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通讯作者：
J. Terradas;I. Arregui;R. Oliver;J. Ballester;J. Andries;M. Goossens
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文献类型：
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作者：
J. Terradas;I. Arregui;R. Oliver;J. Ballester;J. Andries;M. Goossens
本文研究了一个多股直线日冕环模型中横向振荡的激发和阻尼。我们的平衡位形的横向几何形状是相当不规则的，比通常的圆柱环模型更真实。通过数值求解二维的含时理想磁流体动力学方程，我们展示了如何将由外部扰动激发的整个束的全局运动转换为由于共振吸收过程而引起的局部Alfvénic运动。这个过程产生横向振荡的衰减。在结构中的任何位置，都可以找到两个主频率：全局模式或准模式的频率和局部阿尔文频率。我们发现，模式转换的机制，由于快波和阿尔文波之间的耦合，是不妥协的模型的复杂的几何形状。我们还表明，它是可能的，不仅在复合环的外部边缘的能量转换，但也内部的结构。这些结果的影响和它们与观测的关系进行了讨论。
We study the excitation and damping of transverse oscillations in a multistranded model of a straight line-tied coronal loop. The transverse geometry of our equilibrium configuration is quite irregular and more realistic than the usual cylindrical loop model. By numerically solving the time-dependent ideal magnetohydrodynamic equations in two dimensions, we show how the global motion of the whole bundle of strands, excited by an external disturbance, is converted into localized Alfvénic motions due to the process of resonant absorption. This process produces the attenuation of the transverse oscillations. At any location in the structure, two dominant frequencies are found: the frequency of the global mode or quasi-mode, and the local Alfvén frequency. We find that the mechanism of mode conversion, due to the coupling between fast and Alfvén waves, is not compromised by the complicated geometry of the model. We also show that it is possible to have energy conversion not only at the external edge of the composite loop, but also inside the structure. The implications of these results and their relationship with the observations are discussed.