改进的广义PSTD PIC算法中数值切连科夫不稳定性抑制
Improved Numerical Cherenkov Instability Suppression in the Generalized PSTD PIC Algorithm
AI总结：
本文提出一种方法，通过微调横向场以完全消除数值切连科夫不稳定性基本模，同时最小化横向场修正，通过数值计算残余增长率和与WARP模拟的比较验证了其有效性。
摘要：
广义伪谱时域（包括伪谱分析时域）粒子-网格算法在模拟粒子束和等离子体方面具有显著的灵活性，编写良好的代码运行速度合理。然而，在多维模拟相对论束和流等离子体时，它们会受到数值切连科夫不稳定性的影响。先前研究显示，通过略微修改流粒子所见的横向场可以显著降低不稳定性增长速率。本文提出一种方法，完全消除数值切连科夫不稳定性基本模，同时最小化横向场修正。所采用的程序、数值计算残余增长率（来自较弱的高阶不稳定性别名）以及与WARP模拟的比较均被呈现。在某些情况下，线性范围内不存在数值不稳定性。
英文摘要：
The family of generalized Pseudo-Spectral Time Domain (including the Pseudo-Spectral Analytical Time Domain) Particle-in-Cell algorithms offers substantial versatility for simulating particle beams and plasmas, and well written codes using these algorithms run reasonably fast. When simulating relativistic beams and streaming plasmas in multiple dimensions, they are, however, subject to the numerical Cherenkov instability. Previous studies have shown that instability growth rates can be reduced substantially by modifying slightly the transverse fields as seen by the streaming particles . Here, we offer an approach which completely eliminates the fundamental mode of the numerical Cherenkov instability while minimizing the transverse field corrections. The procedure, numerically computed residual growth rates (from weaker, higher order instability aliases), and comparisons with WARP simulations are presented. In some instances, there are no numerical instabilities whatsoever, at least in the linear regime.
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