Comparison Between Fluid Simulation With Test Particles and Hybrid Simulation for the Kelvin‐Helmholtz Instability
Comparison Between Fluid Simulation With Test Particles and Hybrid Simulation for the Kelvin‐Helmholtz Instability
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DOI：
10.1029/2019ja026890
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发表时间：
2019-08
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通讯作者：
Xuanye Ma;P. Delamere;K. Nykyri;B. Burkholder;B. Neupane;R. Rice
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文献类型：
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作者：
Xuanye Ma;P. Delamere;K. Nykyri;B. Burkholder;B. Neupane;R. Rice
通过开尔文-亥姆霍兹（KH）不稳定性对等离子体输运率的定量研究可以提高我们对太阳-风-磁层耦合过程的理解。模拟研究提供了一个广泛的传输率，通过使用不同的测量基于不同的初始条件和不同的等离子体的描述，这使得跨文献比较困难。在这项研究中，KH不稳定性在类似的初始和边界条件下（即，适用于地球的磁层顶环境）是模拟霍尔磁流体力学与测试粒子和混合模拟。两种模拟给出了相似的粒子混合速率。然而，在流体模拟中，等离子体主要通过由KH驱动的重联引起的几个大磁岛传输，而在混合模拟中，磁岛较小且不规则。在KH不稳定性的非线性阶段，可以产生各向异性温度，其中比熵和磁矩不守恒。这可能对KH不稳定性中的次级过程的发展产生重要影响，因为温度不对称可以为波的生长提供自由能。因此，双绝热理论是不适用的，需要更复杂的状态方程来解决中尺度过程（例如，KH不稳定性），以便更好地理解多尺度耦合过程。
A quantitative investigation of plasma transport rate via the Kelvin‐Helmholtz (KH) instability can improve our understanding of solar‐wind‐magnetosphere coupling processes. Simulation studies provide a broad range of transport rates by using different measurements based on different initial conditions and under different plasma descriptions, which makes cross literature comparison difficult. In this study, the KH instability under similar initial and boundary conditions (i.e., applicable to the Earth's magnetopause environment) is simulated by Hall magnetohydrodynamics with test particles and hybrid simulations. Both simulations give similar particle mixing rates. However, plasma is mainly transported through a few big magnetic islands caused by KH‐driven reconnection in the fluid simulation, while magnetic islands in the hybrid simulation are small and patchy. Anisotropic temperature can be generated in the nonlinear stage of the KH instability, in which specific entropy and magnetic moment are not conserved. This can have an important consequence on the development of secondary processes within the KH instability as temperature asymmetry can provide free energy for wave growth. Thus, the double‐adiabatic theory is not applicable and a more sophisticated equation of state is desired to resolve mesoscale process (e.g., KH instability) for a better understanding of the multi‐scale coupling process.