MHD simulations of the in situ generation of kink and sausage waves in the solar corona by collision of dense plasma clumps
MHD simulations of the in situ generation of kink and sausage waves in the solar corona by collision of dense plasma clumps
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DOI：
10.1051/0004-6361/201935539
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发表时间：
2019-05
影响因子：
6.5
通讯作者：
P. Pagano;H. J. Van Damme;P. Antolin;I. De Moortel
中科院分区：
文献类型：
--
作者：
P. Pagano;H. J. Van Damme;P. Antolin;I. De Moortel
上下文。磁流体动力学(MHD)波在日冕中无处不在，其高度结构化的磁场为其传播提供了有效的波导。虽然已经观测到起源于太阳大气较低层的MHD波，但最近的研究表明，一些MHD波可以由密集的反向传播气流的碰撞在原地产生。目标。在这一理论研究中，我们分析了反向传播流碰撞后在日冕中触发扭结模和香肠模传播的机制，以及流的性质如何影响所产生的波的性质。方法：研究方法。为了详细地研究这一机制，我们进行了一系列理想的2D和3D MHD模拟，其中我们改变了反向传播流的性质；通过一种简单的技术来估计扭结和香肠模的幅度，我们研究了它们在MHD波的产生和传播中的作用。结果。我们发现，波幅在很大程度上取决于流动的动能，而扭结或香肠模式的开始则取决于碰撞气泡之间的不对称性。此外，MHD波的初始波长与流的碰撞所产生的磁位形有关。我们还发现，真正的3D系统响应的波幅更小。结论。在这项研究中，我们提出了一种参数空间描述导致日冕中流动碰撞产生MHD波的机制。未来对这些波的观测可以用来了解日冕的等离子体和磁场的性质。
Context. Magnetohydrodynamic (MHD) waves are ubiquitous in the solar corona where the highly structured magnetic fields provide efficient wave guides for their propagation. While MHD waves have been observed originating from lower layers of the solar atmosphere, recent studies have shown that some can be generated in situ by the collision of dense counter-propagating flows. Aims. In this theoretical study, we analyse the mechanism that triggers the propagation of kink and sausage modes in the solar corona following the collision of counter-propagating flows, and how the properties of the flows affect the properties of the generated waves. Methods. To study in detail this mechanism we ran a series of ideal 2D and 3D MHD simulations where we varied the properties of the counter-propagating flows; by means of a simple technique to estimate the amplitudes of the kink and sausage modes, we investigated their role in the generation and propagation of the MHD waves. Results. We find that the amplitude of the waves is largely dependent on the kinetic energy of the flows, and that the onset of kink or sausage modes depends on the asymmetries between the colliding blobs. Moreover, the initial wavelength of the MHD waves is associated with the magnetic configuration resulting from the collision of the flows. We also find that genuine 3D systems respond with smaller wave amplitudes. Conclusions. In this study, we present a parameter space description of the mechanism that leads to the generation of MHD waves from the collision of flows in the corona. Future observations of these waves can be used to understand the properties of the plasma and magnetic field of the solar corona.