Resonantly damped oscillations of two coronal loops
Resonantly damped oscillations of two coronal loops
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DOI：
10.1051/0004-6361/201015525
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发表时间：
2011
影响因子：
6.5
通讯作者：
D. Robertson;M. Ruderman
中科院分区：
文献类型：
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作者：
D. Robertson;M. Ruderman
在太空任务期间，日冕磁环的横向振荡经常被观测到。自首次观测以来，这些振荡一直被用磁管的扭结振荡来解释。有时会观测到两个或更多日冕环的集体振荡。这使得发展几个平行磁管的集体振荡理论变得很有必要。发展这一理论的另一个原因是，有证据表明至少一些日冕环不是整体的，而是由许多细的磁力线组成。本文发展了两个平行磁管扭结振荡的共振阻尼线性理论。利用两个小参数，即管间距离与管长之比以及密度变化区域的厚度与管半径之比，来获得衰减量的渐近表达式。在两个相同管的特殊情况下，明确计算了该表达式。研究了阻尼时间对管间分离距离以及密度对比度的依赖关系。特别是，我们得到管间的相互作用降低了共振吸收的效率。
Transverse oscillations of coronal magnetic loops are routinely observed during the space missions. Since the first observation these oscillations were interpreted in terms of kink oscillations of magnetic tubes. Sometimes collective oscillations of two or more coronal loops are observed. This makes the development of theory of collective oscillations of a few parallel magnetic tubes desirable. Another reason for the development of this theory is that there are evidences that at least some coronal loops are not monolithic but consist of many thin magnetic threads. In this paper the linear theory of resonant damping of kink oscillations of two parallel magnetic tubes is developed. Two small parameters, the ratio of the distance between the tubes to the tube length and the ratio of thickness of regions with varying density to the tube radius, are used to obtain the asymptotic expression for the decrement. This expression is calculated explicitly in a particular case of two identical tubes. The dependence of damping time on the separation distance between the tubes and on the density contrast is investigated. In particular, we obtained that the interaction between the tubes reduces the efficiency of resonant absorption.