TRACE observations of driven loop oscillations
TRACE observations of driven loop oscillations
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驱动环路振荡的 TRACE 观察
DOI：
10.1051/0004-6361/201014265
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发表时间：
2011
影响因子：
6.5
通讯作者：
Ballai I
中科院分区：
文献类型：
--
作者：
Ballai I
1998年6月13日，TRACE卫星碰巧处于观测日冕中耀斑引起的EIT波的影响及其随后与日冕磁环的相互作用的良好位置。在这项研究中，我们使用这些TRACE观测来证实以前的理论工作，它确定了在理想磁流体动力学的背景下，日冕环对谐波驱动器的响应，以及估计磁场强度和纵向不均匀性的程度。通过拟合缩放的正弦函数来分析从其静止状态的相应环位移。结果日冕环具有两个明显的周期，分别为501 ± 5 s和274 ± 7 s，这两个周期可以解释为基本的扭折模和一次谐波，也可以解释为一个过驱动环的阶段。另外还列出了解释这两个时期的其他情景，每一种情景都导致了磁场的不同值以及日冕环的内在和次分辨率特性。当假设周期属于基本扭折模及其一次谐波时，我们得到振荡日冕环内部的磁场强度为2.0 ± 0.7G。相反，将振荡解释为回路的自然扭结频率和谐波EIT波的组合提供了5.8 ± 1.5 G的磁场强度。利用这两个周期的比值，我们发现环中的引力标度高度为73 ± 3 Mm.ConclusionsWe表明，在日冕环中观察到两个不同的周期并不一定会导致一个独特的结论。存在多种可能的情况，表明磁场的导出强度和日冕环的次分辨率特性完全取决于选择哪种解释。解释的观测结果的组合的自然扭结模式的日冕环，驱动的谐波EIT波似乎导致与以前的研究结果一致的磁场值。其他解释，这是现实的，如扭结基模/第一谐波和两个亚分辨率线程的振荡导致磁场强度低于平均值之前发现。
AimsOn 13 June 1998, the TRACE satellite was fortuitously well placed to observe the effects of a flare-induced EIT wave in the corona, and its subsequent interaction with coronal magnetic loops. In this study, we use these TRACE observations to corroborate previous theoretical work, which determined the response of a coronal loop to a harmonic driver in the context of ideal magnetohydrodynamics, as well as estimate the magnetic field strength and the degree of longitudinal inhomogeneity.MethodsLoop edges are tracked, both spatially and temporally, using wavelet modulus maxima algorithms, with corresponding loop displacements from its quiescent state analysed by fitting scaled sinusoidal functions. The physical parameters of the coronal loop are subsequently determined using seismological techniques.ResultsThe studied coronal loop is found to oscillate with two distinct periods, 501 ± 5 s and 274 ± 7 s, which could be interpreted as belonging to the fundamental kink mode and first harmonic, or could reflect the stage of an overdriven loop. Additional scenarios for explaining the two periods are listed, each resulting in a different value of the magnetic field and the intrinsic and sub-resolution properties of the coronal loop. When assuming the periods belong to the fundamental kink mode and its first harmonic, we obtain a magnetic field strength inside the oscillating coronal loop of 2.0 ± 0.7 G. In contrast, interpreting the oscillations as a combination of the loop’s natural kink frequency and a harmonic EIT wave provides a magnetic field strength of 5.8 ± 1.5 G. Using the ratio of the two periods, we find that the gravitational scale height in the loop is 73 ± 3 Mm.ConclusionsWe show that the observation of two distinct periods in a coronal loop does not necessarily lead to a unique conclusion. Multiple plausible scenarios exist, suggesting that both the derived strength of the magnetic field and the sub-resolution properties of the coronal loop depend entirely on which interpretation is chosen. The interpretation of the observations in terms of a combination of the natural kink mode of the coronal loop, driven by a harmonic EIT wave seems to result in values of the magnetic field consistent with previous findings. Other interpretations, which are realistic, such as kink fundamental mode/first harmonic and the oscillations of two sub-resolution threads result in magnetic field strengths that are below the average values found before.
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DOI：
10.1051/0004-6361:20077916
发表时间：
2007
期刊：
Proceedings of the International Astronomical Union
影响因子：
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作者：
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DOI：
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发表时间：
2005
期刊：
影响因子：
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DOI：
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发表时间：
1998
期刊：
影响因子：
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作者：
D. Christian;J. J. Drake;M. Mathioudakis
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影响因子：
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作者：
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影响因子：
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