Abstract

Formation and evolution of a density bump in an electrostatic shock wave during decay of a discontinuity in a plasma characterized by the presence of hot electrons and a large drop in plasma density across the discontinuity are investigated. Numerical particle-in-cell simulation in a wide range of plasma parameters revealed that the appearance of the density bump as a result of the action of the electric field of high-energy electrons in the region of the travelling shock front changes the character of generated ion–acoustic waves and is accompanied by complex nonlaminar kinetics of different fractions of accelerated and thermal ions, including those reflected from the front. Investigation of particle trajectories in real and phase spaces unveiled that ions on both sides of the discontinuity, namely, ions of the rarefied plasma captured by the wave and accelerated ions of the dense plasma catching it up, participate in formation and sustaining of the density bump in the shock wave. A qualitative analysis of contributions of both ion components to the density bump is carried out, and specific features of the latter for typical parameters of laser plasma are found.

中文翻译：

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在热密等离子体膨胀成冷稀疏等离子体的过程中，无碰撞静电冲击波中形成的密度凸点

摘要

研究了在不连续性的衰减过程中，以热电子的存在和整个不连续性中等离子体密度的大幅度下降为特征的静电激波中密度突波的形成和演变。在广泛的等离子体参数中进行的单元格数值模拟表明，由于高能电子在行进的冲击波前沿区域中的电场作用，密度凸点的出现改变了产生的特性。离子声波，并伴有不同比例的加速和热离子的复杂非层流动力学，包括从正面反射的离子。对实相空间和相空间中的粒子轨迹的研究表明，不连续两侧的离子，即 被波捕获的稀有等离子体的离子和被其捕获的密集等离子体的加速离子参与冲击波中密度突波的形成和维持。对这两种离子成分对密度凸点的贡献进行了定性分析，并发现了后者对于激光等离子体典型参数的特定特征。