多尺度等离子体动力学数值模拟中最初的无方程投影积分技术

A Primal Equation Free Projective Integration Scheme in Multi-Scale Plasma Dynamics

发展一种针对等离子体多尺度问题的"最初的无方程投影积分(p-EFPI)"方法并成功应用于离子声波的模拟.该方法包括时间推进和时间投影两部分.电子速度通过概率分布函数或累积分布函数投影外推,电子位置坐标则通过投影外推的电子电荷密度重新调出;与电子相比,假设粗糙的离子运动可以很好地描述宏观尺度等离子体的演化行为,通过追踪和投影外推每个离子轨道保持全部离子运动学效应.尝试和检验p-EFPI方法在模拟等离子体物理现象中的应用.以离子声波为范例,数值计算表明:在离子相空间出现离子捕获效应前,p-EFPI模拟能够很好地再现PIC的结果,在离子捕获发生后,p-EFPI模拟仍然可以抓住除了离子捕获特征之外的其它主要物理特征.

A coarse projective method for simulation of multi-dimensional macroscopic systems, Primal Equation Free Projective Integration （p-EFPI） method, was developed and applied to simulation of plasma ion acoustic wave. The method consists of＇two parts： Time stepper and time projection. For election velocities, probability distribution function or cumulative distribution function are recorded in time to project, while, corresponding electron positions are reloaded （restricted） via electron charge density. Ion motion is assumed inherently coarse-grained as compared to electron dynamics, to describe possibly macro scale plasma evolution sufficiefitly well. To preserve full ion kinetic effects, individual ion orbits are tracked in time and simply extrapolate to project. This is one attempt to test method in p-EFPI framework on plasma physics phenomenon. Our calculations for ion acoustic wave paradigm indicate that p- EFPI simulation follows PIC results nice before ion trapping in phase space appears. However, as ion trapping takes place, main characteristic still keeps, except for ion trapping characteristic.