Kinetic Physics of Homogeneous Turbulence in Collisionless Plasmas

这是美国国家科学基金会和能源部共同资助的一个项目。湍流的多尺度性质给运动模拟带来了严峻的计算挑战。该项目将积极推动等离子体中湍流的全粒子模拟的极限。最近开发的一种并行的、隐式的、全粒子动力学模拟程序将被用来进行模拟，该模拟将显示非线性波长级联到较短波长的长度。该项目的重点是湍流中最不为人所知和最具争议的方面，即从长波湍流到短的动力学尺度的转变，以及在比这个转变更短的波长上的湍流的性质。其目标是解决太阳风中长波长模式如何从惯性范围级联到短波长范围的物理问题。单流体磁流体力学(MHD)模型很好地描述了太阳风的惯性范围，这已被证明是描述太阳风中长波长波动的一种非常有效的方法。观测表明，在惯性范围结束处的光谱断裂处的波数与离子惯性长度相对应。离子惯性长度标志着单流体理论的崩溃，动力学效应在这一区域占主导地位。因此，短波长区域一直是太阳风湍流中最不被了解的部分，许多基本问题，如控制断点的物理机制，还没有完全弄清楚。如何正确对待所谓的？消散范围？浑浊现象普遍存在于等离子体中，存在于星际介质、吸积盘、行星磁层和太阳风等各种环境中。主要的理论焦点一直是长波长湍流，其中MHD是一个很好的近似。这个项目将使用波动湍流理论和最先进的全粒子动力学模拟以及无与伦比的计算资源来研究湍流从惯性范围向下到以哨声波为特征的短波长区域的演变。拟议的活动将加强研究的基础设施。该项目将使用尖端模拟，包括基于单元的技术，以推动完全粒子在单元(PIC)模拟的极限。这些进展将为等离子体物理界过渡到使用基于细胞的计算机进行模拟的新技术铺平道路。这些代码将通过免费的GNU通用公共许可证(V2)通过Google Code项目提供。该网站不仅包括代码和样本输入文件，还包括(I)代码及其方法的简要描述，(Ii)关于如何使用代码的维基百科风格的手册，以及关于如何设置问题和运行它的详细描述，以及(Iii)用于读取和绘制结果的样本图形文件。

The is a jointly funded project between the National Science Foundation and the Department of Energy.The multi-scale nature of turbulence poses a severe computational challenge for kinetic simulations. This project will aggressively push the limits of full particle simulations of turbulence in plasmas. A recently developed parallel, implicit, full particle kinetic simulation code will be used to perform simulations that will show how long wavelength modes non-linearly cascade to shorter wavelengths. The focus of this project is on the least understood and most controversial aspect of turbulence, namely the transition of long wavelength turbulence to short, kinetic scales and the properties of turbulence at wavelengths shorter than this transition. The goal is to address the physics of how the long wavelength modes cascade from the inertial range to the short wavelength range in the solar wind. The inertial range is fairly well described by single-fluid, magnetohydrodynamic (MHD) models, which have proved to be a very effective approach to describing long-wavelength fluctuations in the solar wind. Observations have shown that the wavenumber at the spectral break, where the inertial range ends, corresponds to the ion inertial length. The ion inertial length marks the breakdown of single fluid theory and kinetic effects become dominant in this regime. As a result, the short wavelength regime has remained the least understood component of solar wind turbulence and many basic questions such as the physics controlling the breakpoint are not completely understood. The proper treatment of the so-called ?dissipation range? requires a fully kinetic treatment.Turbulence is ubiquitous in plasmas, occurring in a variety of settings such as interstellar medium, accretion disks, planetary magnetospheres, and the solar wind. The main theoretical focus has been on long wavelength turbulence where MHD is a good approximation. This project will use a tandem of wave turbulence theory and state-of-the-art full particle kinetic simulations with unmatched computational resources to investigate the evolution of turbulence from the inertial range down to the short wavelength regime characterized by whistler waves. The proposed activity will enhance the infrastructure for research. The project will use cutting edge simulations including cell-based technology to push the limits of full particle-in-cell (PIC) simulations. These advances will pave the way for the plasma physics community to transition to new techniques for simulations using cell-based computers. The codes will be made available through a free GNU General Public License (v2), via the Google Code project. The web site will include not only the code and sample input files, but it also include (i) a brief description of the code and its methods, (ii) a wikipedia-style manual on how to use the code with an extensive description on how to set up a problem and run it, and (iii) sample graphics files to read and plot the results.