Scaling the Ion Inertial Length and Its Implications for Modeling Reconnection in Global Simulations: SCALING THE ION INERTIAL LENGTH
Scaling the Ion Inertial Length and Its Implications for Modeling Reconnection in Global Simulations: SCALING THE ION INERTIAL LENGTH
复制标题
缩放离子惯性长度及其对全局模拟中重连接建模的影响：缩放离子惯性长度
DOI：
10.1002/2017ja024189
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
Peng, Ivy Bo
中科院分区：
文献类型：
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作者：
Tóth, Gábor;Chen, Yuxi;Gombosi, Tamas I.;Cassak, Paul;Markidis, Stefano;Peng, Ivy Bo
我们调查使用人为增加的离子和电子动力学尺度在全球等离子体模拟。我们认为，只要整体和离子惯性尺度保持良好的分离，（1）整体解对离子惯性尺度的值并不强烈敏感，而（2）离子惯性尺度动力学也将类似于原始系统，但它发生在更大的空间尺度上，（3）中间尺度的结构，如磁岛，以自相似的方式生长。为了研究我们的标度假设的有效性和局限性，我们进行了许多模拟的二维磁层与嵌入粒子的磁流体动力学（MHD-EPIC）模型。PIC模型涵盖了昼侧重联站点。模拟结果证实，只要增加的离子惯性长度保持在磁层顶距离的5%以下，假设是正确的。由于理论论证是一般性的，我们希望这些结果可以推广到三维空间。在二维和三维模拟中，计算成本分别降低了比例因子的三次方和四次方，这可以是许多数量级。目前的研究结果表明，全球模拟解决重联动力学尺度是可行的。这是应用于地球、土星和木星磁层以及日冕的关键一步。
We investigate the use of artificially increased ion and electron kinetic scales in global plasma simulations. We argue that as long as the global and ion inertial scales remain well separated, (1) the overall global solution is not strongly sensitive to the value of the ion inertial scale, while (2) the ion inertial scale dynamics will also be similar to the original system, but it occurs at a larger spatial scale, and (3) structures at intermediate scales, such as magnetic islands, grow in a self‐similar manner. To investigate the validity and limitations of our scaling hypotheses, we carry out many simulations of a two‐dimensional magnetosphere with the magnetohydrodynamics with embedded particle‐in‐cell (MHD‐EPIC) model. The PIC model covers the dayside reconnection site. The simulation results confirm that the hypotheses are true as long as the increased ion inertial length remains less than about 5% of the magnetopause standoff distance. Since the theoretical arguments are general, we expect these results to carry over to three dimensions. The computational cost is reduced by the third and fourth powers of the scaling factor in two‐ and three‐dimensional simulations, respectively, which can be many orders of magnitude. The present results suggest that global simulations that resolve kinetic scales for reconnection are feasible. This is a crucial step for applications to the magnetospheres of Earth, Saturn, and Jupiter and to the solar corona.