Monte Carlo二体碰撞粒子模拟中的数值加热
Numerical heating in particle-in-cell simulations with Monte Carlo binary collisions
摘要：
二进制蒙特卡罗（MC）碰撞算法是一个标准的和强大的方法，包括二进制库仑碰撞效应的粒子在细胞（PIC）模拟的等离子体。在这里，我们表明，PIC和MC算法之间的耦合可以引起系统的（非物理）数值加热，显着超过这些算法独立运行时观察到的。我们认为，这种有害的影响的结果与MC碰撞和集体电磁场的PIC网格上执行的工作的粒子运动之间的不一致。这种不一致性表现为电磁能的（人工）随机产生，最终加热等离子体粒子。MC诱导的数值加热可显著影响长模拟时间（典型数值参数的$\gtrsim 10^3$碰撞周期）模拟系统的演化。我们描述的MC诱导的数值加热的来源分析，并讨论策略，以尽量减少它。
英文摘要：
The binary Monte Carlo (MC) collision algorithm is a standard and robust method to include binary Coulomb collision effects in particle-in-cell (PIC) simulations of plasmas. Here, we show that the coupling between PIC and MC algorithms can give rise to (nonphysical) numerical heating of the system, that significantly exceeds that observed when these algorithms operate independently. We argue that this deleterious effect results from an inconsistency between the particle motion associated with MC-collisions and the work performed by the collective electromagnetic field on the PIC grid. This inconsistency manifests as the (artificial) stochastic production of electromagnetic energy, which ultimately heats the plasma particles. The MC-induced numerical heating can significantly impact the evolution of the simulated system for long simulation times ($\gtrsim 10^3$ collision periods, for typical numerical parameters). We describe the source of the MC-induced numerical heating analytically and discuss strategies to minimize it.
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