Turbulence Dynamics in the Presence of Flow Shear in a Collisional Plasma: Experiment-Model Cross-Validation

这个项目旨在通过对大规模计算机模型与精心控制的实验室实验进行详细的比较，进一步加深我们对等离子体湍流和流动的基本理解。湍流及其效应在地球、近空间和整个宇宙的磁化等离子体中无处不在。湍流可以推动粒子、热量和动量的传输，这会影响我们在地球上应用等离子体的能力，例如聚变能，并且可以在加速粒子到高能量方面发挥重要作用，例如在包括太阳和地球的空间天气环境中。空间天气事件产生的大量高能粒子有可能严重影响地球上的卫星、通信和电力系统。 要能够可靠地预测这些事件，需要对底层物理学有详细的了解，包括湍流的物理学以及湍流和流动的相互作用。这项工作的目标是验证，通过控制实验室实验和密切的实验理论模型耦合，一个完全全球性的，非线性的双流体模型，适合于理解湍流和运输动力学在碰撞实验室等离子体。尽管有长期和持续的工作历史，以了解剪切流存在下的等离子体湍流的动力学，似乎仍然没有经过验证的模型，可以准确地再现实验观察到的各种湍流状态，即使是相对简单的，控制良好的实验。即使在这些“简单”的实验室实验中，也存在足够复杂的物理学，因此纯粹通过准线性理论或局部非线性模型来解释测量似乎是困难或不可能的。拟议的实验将在新墨西哥州大学的双源HelCat（Helicon-Cathode）设备中进行。HelCat是一种灵活的设备，可提供对这些实验至关重要的独特功能。GBS（Global Braginskii Solver）是一种全三维全局漂移减少的Braginskii求解器，以前曾用于对线性和环形器械进行建模，将用于对这些实验进行建模。实验模型的比较将在广泛的条件下进行，从相干到充分发展的湍流状态。

This project seeks to further our fundamental understanding of plasma turbulence and flows by making detailed comparisons of large-scale computer models with carefully controlled laboratory experiments. Turbulence and its effects are ubiquitous in magnetized plasmas on Earth, in near space, and throughout the universe. Turbulence can drive increased transport of particles, heat, and momentum, which affects our ability to confine plasmas for applications on Earth, such as fusion energy, and can play an important role in accelerating particles to high energies, for example in the space weather environment comprising the Sun and Earth. The large numbers of high energy particles generated during space weather events have the potential to seriously impact satellites, communications, and power systems on Earth. Being able to reliably predict such events requires a detailed understanding of the underlying physics, including the physics of turbulence and the interaction of turbulence and flows. The goal of this work is to validate, through controlled laboratory experiments and close experiment-theory-model coupling, a fully global, nonlinear two-fluid model appropriate for understanding turbulence and transport dynamics in a collisional laboratory plasma. Despite a long and ongoing history of work to understand the dynamics of plasma turbulence in the presence of sheared flows, there still appears to be no validated model that can accurately reproduce experimental observations over a wide range of turbulent states in even relatively simple, well-controlled experiments. Even in these 'simple' laboratory experiments, enough complicating physics are present so that interpreting measurements purely experimentally, via quasilinear theories, or via local nonlinear models seems to be difficult or impossible. The proposed experiments will take place in the dual-source HelCat (Helicon-Cathode) device at the University of New Mexico. HelCat is a flexible device that provides unique capabilities important to these experiments. The GBS (Global Braginskii Solver), a fully 3D global drift-reduced Braginskii solver that has been used previously to model both linear and toroidal devices will be used to model these experiments. Experiment-model comparisons will be undertaken under a wide range of conditions, from coherent to fully-developed turbulent states.