Two-way coupling of a global Hall magnetohydrodynamics model with a local implicit particle-in-cell model
Two-way coupling of a global Hall magnetohydrodynamics model with a local implicit particle-in-cell model
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DOI：
10.1016/j.jcp.2014.03.009
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发表时间：
2014-07
期刊：
影响因子：
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通讯作者：
L. Daldorff;G. Tóth;T. Gombosi;G. Lapenta;J. Amaya;S. Markidis;J. Brackbill
中科院分区：
文献类型：
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作者：
L. Daldorff;G. Tóth;T. Gombosi;G. Lapenta;J. Amaya;S. Markidis;J. Brackbill
基于等离子体流体描述的计算模型，如磁流体力学(MHD)和扩展磁流体力学(XMHD)程序，效率很高，但由于假设陀螺半径小、电荷中性和麦克斯韦热速度分布，它们忽略了动力学效应。动力学代码可以适当地考虑动力学效应，但由于自由度的增加，它们比流体代码贵几个数量级。如果流体描述在计算领域的很大一部分中是可接受的，则将动力学模型限制在动力学效应重要的区域是有意义的。这种耦合方法比纯动力学模型效率高得多。假设动力学代码使用统一的网格，则加速大约是整个区域相对于动力学区域的体积比。文献[1]提出了这一思想，但它们的耦合限于一维，并且在流体和动力学模型中采用了截然不同的网格分辨率。我们描述了Hall MHD模型BATS-R-US和隐式粒子在单元(PIC)模型iPIC3D之间的全二维双向耦合。可以用相同的网格分辨率和时间步长进行耦合。我们称这种耦合计算等离子体模型为MHD-EPIC(嵌入PIC区域的MHD)。验证测试表明，MHD-EPIC算法具有较高的准确性和健壮性。我们给出了一个二维磁层模拟作为MHD-EPIC潜在的未来应用的例证。
Computational models based on a fluid description of the plasma, such as magnetohydrodynamic (MHD) and extended magnetohydrodynamic (XMHD) codes are highly efficient, but they miss the kinetic effects due to the assumptions of small gyro radius, charge neutrality, and Maxwellian thermal velocity distribution. Kinetic codes can properly take into account the kinetic effects, but they are orders of magnitude more expensive than the fluid codes due to the increased degrees of freedom. If the fluid description is acceptable in a large fraction of the computational domain, it makes sense to confine the kinetic model to the regions where kinetic effects are important. This coupled approach can be much more efficient than a pure kinetic model. The speed up is approximately the volume ratio of the full domain relative to the kinetic regions assuming that the kinetic code uses a uniform grid. This idea has been advocated by [1] but their coupling was limited to one dimension and they employed drastically different grid resolutions in the fluid and kinetic models.We describe a fully two-dimensional two-way coupling of a Hall MHD model BATS-R-US with an implicit Particle-in-Cell (PIC) model iPIC3D. The coupling can be performed with identical grid resolutions and time steps. We call this coupled computational plasma model MHD-EPIC (MHD with Embedded PIC regions). Our verification tests show that MHD-EPIC works accurately and robustly. We show a two-dimensional magnetosphere simulation as an illustration of the potential future applications of MHD-EPIC.