Dipartimento di Fisica, Università della Calabria, 87036, Rende (Cosenza), Italy.
Phys Rev E. 2018 May;97(5-1):053212. doi: 10.1103/PhysRevE.97.053212.
The hybrid Vlasov-Maxwell system of equations is suitable to describe a magnetized plasma at scales on the order of or larger than proton kinetic scales. An exact stationary solution is presented by revisiting previous results with a uniform-density shear flow, directed either parallel or perpendicular to a uniform magnetic field, and by adapting the solution to the hybrid Vlasov-Maxwell model. A quantitative characterization of the equilibrium distribution function is provided by studying both analytically and numerically the temperature anisotropy and gyrotropy and the heat flux. In both cases, in the shear region, the velocity distribution significantly departs from local thermodynamical equilibrium. A comparison between the time behavior of the usual "fluidlike" equilibrium shifted Maxwellian and the exact stationary solutions is carried out by means of numerical simulations of the hybrid Vlasov-Maxwell equations. These hybrid equilibria can be employed as unperturbed states for numerous problems which involve sheared flows, such as the wave propagation in an inhomogeneous background and the onset of the Kelvin-Helmholtz instability.
混合的 Vlasov-Maxwell 方程组适用于描述在质子动理学尺度或更大的量级上的磁化等离子体。通过对具有均匀密度切向流的先前结果进行重新研究，该方程组给出了一个精确的稳定解，该切向流的方向可以与均匀磁场平行或垂直，并将该解应用于混合的 Vlasov-Maxwell 模型。通过分析和数值研究温度各向异性、旋度和热通量，对平衡分布函数进行了定量描述。在这两种情况下，在切变区域，速度分布明显偏离局部热力学平衡。通过混合的 Vlasov-Maxwell 方程组的数值模拟，对通常的“类流体”平衡偏移麦克斯韦尔分布和精确的稳定解的时间行为进行了比较。这些混合平衡可以作为涉及切变流的众多问题的未扰状态，例如在不均匀背景中波的传播和开尔文-亥姆霍兹不稳定性的发生。
