含有慢驻波的太阳大气结构的稳定性：可压缩等离子体中的分析模式
Stability of solar atmospheric structures harboring standing slow waves: An analytical model in a compressible plasma
摘要：
内容：在太阳日冕加热问题的背景下，对高日冕温度的一个可能的解释是磁流体动力学（MHD）波的能量释放。能量转移被认为是可能的，除其他外，在日冕环的开尔文-亥姆霍兹不稳定性（KHI）的发展。目的：我们的目的是确定如果在太阳大气结构，如日冕环，以及突出线程，太阳黑子和孔隙，可以触发KHI由于振荡剪切流在结构的边界。方法：采用线性化的非平稳磁流体动力学方法，建立了一个磁流体参考系的解析模型。该模型描述了一个可压缩的等离子体附近的不连续的界面分离的两个区域的均匀等离子体，每个窝藏一个振荡的速度场具有恒定的振幅，这是平行于背景磁场和接口对齐。然后，利用所获得的分析结果来确定所述界面在日冕和光球条件下的稳定性。结果：发现界面的稳定性由Mathieu方程决定。根据该方程的参数，界面可以是稳定的或不稳定的。对于日冕以及光球的条件下，我们发现，接口是稳定的KHI。然而，理论上，它可以相对于参数共振不稳定性是不稳定的，尽管这在物理上似乎不太可能。我们的结论是，在这个简化的设置，一个驻波慢波不触发的KHI没有参与额外的物理过程。
英文摘要：
Context: In the context of the solar coronal heating problem, one possible explanation for the high coronal temperature is the release of energy by magnetohydrodynamic (MHD) waves. The energy transfer is believed to be possible, among others, by the development of the Kelvin-Helmholtz instability (KHI) in coronal loops. Aims: Our aim is to determine if standing slow waves in solar atmospheric structures such as coronal loops, and also prominence threads, sunspots, and pores, can trigger the KHI due to the oscillating shear flow at the structure's boundary. Methods: We used linearized nonstationary MHD to work out an analytical model in a cartesian reference frame. The model describes a compressible plasma near a discontinuous interface separating two regions of homogeneous plasma, each harboring an oscillating velocity field with a constant amplitude which is parallel to the background magnetic field and aligned with the interface. The obtained analytical results were then used to determine the stability of said interface, both in coronal and photospheric conditions. Results: We find that the stability of the interface is determined by a Mathieu equation. In function of the parameters of this equation, the interface can either be stable or unstable. For coronal as well as photospheric conditions, we find that the interface is stable with respect to the KHI. Theoretically, it can, however, be unstable with respect to a parametric resonance instability, although it seems physically unlikely. We conclude that, in this simplified setup, a standing slow wave does not trigger the KHI without the involvement of additional physical processes.
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