通过涡脱落的横向环振荡：一个自振荡过程
Transverse loop oscillations via vortex shedding: a self oscillating process
摘要：
确定日冕环中横向振荡激发背后的基本机制对于它们作为日冕地震学诊断工具的作用以及它们作为日冕波加热机制的潜在用途至关重要。在本文中，我们探讨的概念，这些横向振荡被激发通过一个自我维持的过程中，所造成的Alfvénic涡脱落从强背景流与日冕环相互作用。我们第一次在三维模拟中表明，旋涡脱落可以在冠状环中产生横向振荡，在垂直于流动的方向上，由于周期性的“推动”的旋涡。通过绘制功率谱密度，我们确定这些振荡的激发频率。我们看到，这些频率既取决于流速，也取决于振荡回路的特性。除了背景流是恒定的而不是周期性的这一事实之外，这使得我们将其视为自振荡过程。最后，激发的振荡的振幅是接近恒定的振幅，并与无衰减振荡的观察。这使得正在考虑的机制可能解释这些无阻尼波在冕环。
英文摘要：
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 Alfvénic 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.
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