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Transverse Loop Oscillations via Vortex Shedding: A Self-oscillating Process
The Astrophysical Journal Letters ( IF 7.9 ) Pub Date : 2021-02-10 , DOI: 10.3847/2041-8213/abdc2b
Konstantinos Karampelas 1, 2 , Tom Van Doorsselaere 2
Affiliation  

Identifying the underlying mechanisms behind the excitation of transverse oscillations in coronal loops is essential for their role as diagnostic tools in coronal seismology and their potential use as wave heating mechanisms of the solar corona. In this paper, we explore the concept of these transverse oscillations being excited through a self-sustaining process, caused by Alfvnic vortex shedding from strong background flows interacting with coronal loops. We show for the first time in 3D simulations that vortex shedding can generate transverse oscillations in coronal loops, in the direction perpendicular to the flow due to periodic “pushing” by the vortices. By plotting the power spectral density we identify the excited frequencies of these oscillations. We see that these frequencies are dependent both on the speed of the flow, as well as the characteristics of the oscillating loop. This, in addition to the fact that the background flow is constant and not periodic, makes us treat this as a self-oscillating process. Finally, the amplitudes of the excited oscillations are near constant in amplitude, and are comparable with the observations of decay-less oscillations. This makes the mechanism under consideration a possible interpretation of these undamped waves in coronal loops.



中文翻译:

通过涡流脱落的横向环路振荡:一种自振荡过程

查明日冕环中横向振荡激发背后的潜在机制,对于它们在日冕地震学中的诊断工具的作用及其作为太阳日冕电波加热机制的潜在用途至关重要。在本文中,我们探讨了由自支撑过程激发的横向振荡的概念,这种横向振荡是由强背景流与冠状环相互作用引起的Alfvnic涡旋脱落引起的。我们首次在3D模拟中显示,由于周期性的周期性“推动”,涡旋脱落会在冠状环中产生垂直于流动方向的横向振荡。通过绘制功率谱密度,我们可以确定这些振荡的激发频率。我们看到这些频率既取决于流动速度,以及振荡回路的特性。除了背景流量是恒定的而且不是周期性的事实之外,这使我们将此视为自激过程。最后,激发振荡的振幅在振幅上接近恒定,并且与无衰减振荡的观察结果相当。这使得所考虑的机制可能解释了冠状环中这些未衰减的波。

更新日期:2021-02-10
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