GEM: Anti-Parallel and Component Merging Scenarios in Collisionless Reconnection

最近的工作已经导致了一些令人惊讶的结果，挑战了许多关于磁重联的基本物理学的传统观点。这个项目将重新研究物理重联利用粒子在细胞等离子体模拟代码。模拟的一个重要方面是，它们将使用开放边界模型而不是传统的周期性边界条件运行。这种方法的初步结果似乎很有希望，因为人工再循环是固有的周期性边界条件被完全消除。 允许等离子体和磁通量根据需要进出系统。由此产生的模拟有效地模拟了一个更大的系统比可能与周期性的边界条件。这些模拟导致了一个新的理解的电子扩散区的结构和快速重联的影响。该代码的一个创新方面是，它已被改编为基于细胞的计算机，这可能是未来的大规模计算与预期的速度增益的一个因素，40比现有的模拟。该项目将研究与地球空间环境建模计划的重点小组有关的几个重要问题。 拟调查的具体专题包括：（1）反平行重联与分量合并的相对作用，（2）等离子体湍流对重联速率的作用，（3）重联的起始及其随后的非线性发展对等离子体β参数的依赖性（等离子体压力与磁压力之比），以及（4）在重联区的不对称电流片的演变。该项目的教育方面包括支持几个本科生在UCSD参与了这项研究。爱荷华州大学的两名研究生也将参与其中。

Recent work has led to a number of surprising results that challenge many of the conventional viewpoints regarding the essential physics of magnetic reconnection. This project will re-examine the physics of reconnection utilizing a Particle-In-Cell plasma simulation code. An important aspect of the simulations is that they will be run using an open boundary model rather than the traditional periodic boundary condition. The initial results from this approach appear quite promising since the artificial recirculation that is inherent with periodic boundary conditions is completely eliminated. Plasma and magnetic flux is allowed to enter and exit the system as needed. The resulting simulations effectively mimic a much larger system than is possible with periodic boundary conditions. These simulations have led to a new understanding of the structure of the electron diffusion region and its effect on fast reconnection. An innovative aspect of the code is that it has been adapted for cell-based computers which are likely to be the future of large-scale computations with expected speed gains of a factor of 40 over existing simulations. The project will examine several important questions related to magnetic reconnection that are relevant to the Geospace Environment Modeling program's focus groups. The specific topics to be investigated include: (1) the relative roles of anti-parallel reconnection versus component merging, (2) the role of plasma turbulence on the rate of reconnection, (3) the dependence of the onset of reconnection and its subsequent nonlinear development on the plasma beta parameter (the ratio of the plasma pressure to the magnetic pressure), and (4) the evolution of asymmetric current sheets in the reconnection region.The educational aspects of the project includes support for several undergraduate students at UCSD to participate in the research. Two graduate students at the University of Iowa will also be involved.