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首页> 外文期刊>Plasma physics and controlled fusion >DK-1D: a drift-kinetic simulation tool for modelling the shear Alfven wave and its interaction with collisionless plasma
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DK-1D: a drift-kinetic simulation tool for modelling the shear Alfven wave and its interaction with collisionless plasma

机译：DK-1D：用于模拟Alfven剪切波及其与无碰撞等离子体相互作用的漂移动力学仿真工具

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摘要

We present a highly accurate tool for the simulation of shear Alfven waves (SAWs) in collisionless plasma. SAW are important in space plasma environments because for small perpendicular scale lengths they can support an electric field parallel to the ambient magnetic field. Electrons can be accelerated by the parallel electric field and these waves have been implicated as the source of vibrant auroral displays. However, the parallel electric field carried by SAW is small in comparison with the perpendicular electric field of the wave, making it difficult to measure directly in the laboratory, or by satellites in the near-Earth plasma environment. In this paper, we present a simulation code that provides a means to study in detail the SAW -particle interaction in both space and laboratory plasma. Using idealized, small-amplitude propagating waves with a single perpendicular wavenumber, the simulation code accurately reproduces the damping rates and parallel electric field amplitudes predicted by linear theory for varying temperatures and perpendicular scale lengths. We present a rigorous kinetic derivation of the parallel electric field strength for small-amplitude SAW and show that commonly used inertial and kinetic approximations are valid except for where the ratio of thermal to Alfven speed is between 0.7 and 1.0. We also present nonlinear simulations of large-amplitude waves and show that in the cases of strong damping, the damping rates and parallel electric field strength deviate from linear predictions when wave energies are greater than only a few per cent of the plasma kinetic energy, a situation which is often observed in the magnetosphere. The drift-kinetic code provides reliable, testable predictions of the parallel electric field strength which can be investigated directly in the laboratory, and will help to bridge the gap between studies of SAW in man-made and naturally occurring plasma.
机译：我们提供了一种用于在无碰撞等离子体中模拟Alfven剪切波（SAW）的高精度工具。 SAW在空间等离子环境中很重要，因为对于较小的垂直标度长度，它们可以支持平行于环境磁场的电场。电子可以通过平行电场来加速，并且这些波被认为是充满活力的极光显示的来源。然而，与波的垂直电场相比，声表面波所携带的平行电场很小，因此很难直接在实验室或近地等离子体环境中通过卫星进行测量。在本文中，我们提供了一个模拟代码，该代码提供了一种手段来详细研究空间和实验室血浆中的SAW-粒子相互作用。通过使用具有单个垂直波数的理想化，小振幅传播波，该仿真代码可以准确地再现通过线性理论针对变化的温度和垂直刻度长度预测的阻尼率和平行电场幅度。对于小振幅声表面波，我们给出了平行电场强度的严格动力学推导，并表明常用的惯性和动力学近似是有效的，除了热与Alfven速度之比在0.7和1.0之间。我们还提出了大振幅波的非线性模拟，并表明在强阻尼的情况下，当波能量仅大于等离子体动能的百分之几时，阻尼率和平行电场强度就会偏离线性预测。在磁层中经常观察到的情况。漂移动力学代码提供了对平行电场强度的可靠，可测试的预测，可以直接在实验室中进行研究，这将有助于弥合人造和自然存在的等离子体中声表面波研究之间的差距。

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