Application of the theory of damping of kink oscillations by radiative cooling of coronal loop plasma
Application of the theory of damping of kink oscillations by radiative cooling of coronal loop plasma
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DOI：
10.1051/0004-6361/201014504
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发表时间：
2010-09
影响因子：
6.5
通讯作者：
R. Morton;R. Erdélyi
中科院分区：
文献类型：
--
作者：
R. Morton;R. Erdélyi
目标。在这里，我们提出了第一个观察到的众多快速扭结振荡的阻尼和它们的阻尼由于冷却的日冕环的理论模型之间的比较研究。扭折振荡的阻尼理论，由于辐射的太阳等离子体与随时间变化的背景在这里适用于所有已知的情况下，日冕扭折振荡。方法.最近的一个冷却日冕环的动力学模型预测，由于辐射冷却过程，这种环的横向振荡可能会被显着阻尼（Morton & Erdelyi 2009，ApJ，707，750）。回路等离子体的冷却也具有扭结振荡具有时间依赖性频率的结果。该理论适用于一个相对较大的已知的和报告的例子的TRACE观测阻尼扭结振荡。结果我们发现，对于典型的EUV回路（500-2000 s）的冷却时间尺度，所观察到的横向（即扭结）振荡的阻尼几乎可以完全由一半的例子中的冷却过程来解释。似乎不需要其他耗散机制来模拟阻尼。在其余的其他示例中，冷却过程似乎不能完全解释所观察到的阻尼，但仍可能对阻尼产生显著影响。在这些情况下，可能另外需要另一种机制（例如，共振吸收）来解释振荡的完全衰减。此外，我们表明，由于背景等离子体的动态性质，允许随时间变化的频率提供了一个更好的拟合配置文件的观测数据点比一个固定的频率拟合配置文件，打开新的途径，太阳磁震学。
Aims. We present here a first comparative study between the observed damping of numerous fast kink oscillations and the theoretical model of their damping due to the cooling of coronal loops. The theory of damping of kink oscillations due to radiation of the solar plasma with a temporally varying background is applied here to all known cases of coronal kink oscillations. Methods. A recent dynamic model of cooling coronal loops predicts that transverse oscillations of such loops could be significantly damped due to the radiative cooling process (Morton & Erdelyi 2009, ApJ, 707, 750). The cooling of the loop plasma also has the consequence that the kink oscillation has a time-dependent frequency. The theory is applied to a relatively large number of known and reported examples of TRACE observations of damped kink oscillations. Results. We find that, for cooling timescales that are typical of EUV loops (500-2000 s), the observed damping of the transversal (i.e. kink) oscillations can be accounted for almost entirely by the cooling process in half of the examples. No other dissipative mechanism(s) seems to be needed to model the damping. In the remaining other examples, the cooling process does not appear to be able to account fully for the observed damping, though could still have a significant influence on the damping. In these cases another mechanism(s), e.g. resonant absorption, may be additionally required to account for the complete decay of oscillations. Also, we show that because of the dynamic nature of the background plasma, allowing for a time-dependent frequency provides a better fit profile for the data points of observations than a fit profile with a constant frequency, opening novel avenues for solar magneto-seismology.