剪切流磁化等离子体的精确混合动力学平衡

G. Guzzi, A. Settino, F. Valentini, F. Malara
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引用次数: 1

摘要

上下文。以剪切流为特征的磁化等离子体存在于许多自然环境中,例如地球的磁层顶和太阳风。有关等离子体的无碰撞特性需要动力学描述。当剪切层宽度为离子尺度数量级时,可采用混合Vlasov-Maxwell方法。目标本文的目的是推导出具有平面剪切流的磁化等离子体的固定构型的显式形式,在混合Vlasov-Maxwell描述中。考虑了两种结构:第一种是均匀的磁场,斜向体速度;第二种是等量级可变方向磁场。方法。结合研究粒子动力学导出的单粒子运动常数,得到了平稳离子分布函数。考虑背景电磁场的局部近似,对分布函数形式的初步信息进行了解析推导。然后,建立了一种求解一般剖面的数值方法。结果。所发现的显式分布函数允许得到密度、体速度、温度和热流密度的分布。并对分布函数的各向异性和各向异性进行了评价。在均匀斜磁场情况下,验证了数值模拟过程中解的平稳性。结论。所考虑的结构可以用作模拟开尔文-亥姆霍兹不稳定性时地球磁层顶的模型。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Exact hybrid-kinetic equilibria for magnetized plasmas with shearing flows
Context. Magnetized plasmas characterized by shearing flows are present in many natural contexts, such as the Earth's magnetopause and the solar wind. The collisionless nature of involved plasmas requires a kinetic description. When the width of the shear layer is of the order of ion scales, the Hybrid Vlasov-Maxwell approach can be adopted. Aims. The aim of the paper is to derive explicit forms for stationary configurations of magnetized plasmas with planar shearing flows,within the Hybrid Vlasov-Maxwell description. Two configurations are considered: the first with a uniform magnetic field obliquely directed with respect to the bulk velocity; and the second with a uniform-magnitude variable-direction magnetic field. Methods. Stationary ion distribution functions are obtained by combining single-particle constant of motions, which are derived studying particle dynamics. Preliminary information about the form of the distribution functions are analytically derived considering a local approximation for the background electromagnetic field. Then, a numerical method is set up to obtain a solution for general profiles. Results. The explicit distribution functions that are found allow to obtain profiles of density, bulk velocity, temperature and heat flux. Anisotropy and agyrotropy in the distribution function are also evaluated. Stationarity of the solution during numerical simulations is checked in the uniform oblique magnetic field case. Conclusions. The considered configurations can be used as models for the Earth's magnetopause in simulations of the Kelvin-Helmholtz instability.
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