Relativistic magnetic reconnection is a non-ideal plasma process that is a source of non-thermal particle acceleration in many high-energy astrophysical systems. Particle-in-cell (PIC) methods are commonly used for simulating reconnection from first principles. While much progress has been made in understanding the physics of reconnection, especially in 2D, the adoption of advanced algorithms and numerical techniques for efficiently modeling such systems has been limited. With the GPU-accelerated PIC code WarpX, we explore the accuracy and potential performance benefits of two advanced Maxwell solver algorithms: a non-standard finite difference scheme (CKC) and an ultrahigh-order pseudo-spectral method (PSATD). We find that for the relativistic reconnection problem, CKC and PSATD qualitatively and quantitatively match the standard Yee-grid finite-difference method. CKC and PSATD both admit a time step that is 40% longer than Yee, resulting in a ~40% faster time to solution for CKC, but no performance benefit for PSATD when using a current deposition scheme that satisfies Gauss's law. Relaxing this constraint maintains accuracy and yields a 30% speedup. Unlike Yee and CKC, PSATD is numerically stable at any time step, allowing for a larger time step than with the finite-difference methods. We found that increasing the time step 2.4-3 times over the standard Yee step still yields accurate results, but only translates to modest performance improvements over CKC due to the current deposition scheme used with PSATD. Further optimization of this scheme will likely improve the effective performance of PSATD.

翻译：相对论性磁重联是一种非理想等离子体过程，是许多高能天体物理系统中非热粒子加速的来源。粒子网格（PIC）方法通常用于从头模拟重联过程。尽管在理解重联物理（尤其是二维情况）方面取得了重大进展，但采用先进算法和数值技术来高效建模此类系统的研究仍然有限。我们利用GPU加速的PIC代码WarpX，探索了两种先进麦克斯韦求解器算法的精度和潜在性能优势：非标准有限差分格式（CKC）和超高阶伪谱方法（PSATD）。我们发现，对于相对论性重联问题，CKC和PSATD在定性和定量上与标准Yee网格有限差分方法匹配。CKC和PSATD均允许比Yee方法长40%的时间步长，从而为CKC带来约40%的求解加速，但对于采用满足高斯定律的电流沉积方案的PSATD，并未带来性能提升。放宽此约束可保持精度，并带来30%的加速。与Yee和CKC不同，PSATD在任何时间步长下均数值稳定，允许比有限差分方法更大的时间步长。我们发现，将时间步长增加到标准Yee步长的2.4-3倍仍能获得精确结果，但由于PSATD使用的电流沉积方案，其性能提升相对于CKC而言较为有限。进一步优化该方案可能会提高PSATD的有效性能。