Abstract Particle-In-Cell codes are widely used for plasma physics simulations. It is often the case that particles within a computational cell need to be split to improve the statistics or, in the case of non-uniform meshes, to avoid the development of fictitious self-forces. Existing particle splitting methods are largely empirical and their accuracy in preserving the distribution function has not been evaluated in a quantitative way. Here we present a new method specifically designed for codes using adaptive mesh refinement. Although we point out that an exact, distribution function preserving method does exist, it requires a large number of split particles and its practical use is limited. We derive instead a method that minimizes the cost function representing the distance between the assignment function of the original particle and that of the sum of split particles. Depending on the interpolation degree and on the dimension of the problem, we provide tabulated results for the weight and position of the split particles. This strategy represents no overhead in computing time and for a large enough number of split-particles it asymptotically tends to the exact solution.

中文翻译：

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一种在 Particle-In-Cell 代码中调度分裂粒子的新方法

摘要 Particle-In-Cell 代码广泛用于等离子体物理模拟。通常情况下，需要拆分计算单元内的粒子以改善统计数据，或者在非均匀网格的情况下，避免产生虚构的自力。现有的粒子分裂方法在很大程度上是经验性的，它们在保留分布函数方面的准确性尚未以定量方式进行评估。在这里，我们提出了一种专门为使用自适应网格细化的代码设计的新方法。虽然我们指出确实存在一种精确的、保持分布函数的方法，但它需要大量的分裂粒子，其实际应用受到限制。我们推导出一种方法，该方法最小化表示原始粒子的分配函数与分裂粒子总和的分配函数之间的距离的成本函数。根据插值度和问题的维度，我们提供分裂粒子的权重和位置的列表结果。这种策略不代表计算时间的开销，并且对于足够多的分裂粒子，它渐近地趋于精确解。