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

该项目旨在通过将大型计算机模型与精心控制的实验室实验进行详细比较，进一步加深我们对等离子体湍流和流动的基本理解。湍流及其影响在地球、近太空和整个宇宙的磁化等离子体中无处不在。湍流可以增加粒子、热量和动量的传输，这影响了我们限制等离子体在地球上应用的能力，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，例如在由太阳和地球组成的空间天气环境中。在空间天气事件中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。为了能够可靠地预测这些事件，需要对潜在的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。这项工作的目标是通过受控的实验室实验和紧密的实验-理论-模型耦合来验证一个完全全局的非线性双流体模型，该模型适用于理解碰撞实验室等离子体中的湍流和输运动力学。尽管在了解剪切流存在下等离子体湍流动力学方面已经进行了长期和持续的工作，但似乎仍然没有一个经过验证的模型可以在相对简单、控制良好的实验中准确地再现大范围湍流状态下的实验观察结果。即使在这些“简单”的实验室实验中，也存在足够复杂的物理现象，以至于通过拟线性理论或局部非线性模型来解释纯实验测量似乎是困难或不可能的。拟议中的实验将在新墨西哥大学的双源HelCat（螺旋阴极）装置中进行。HelCat是一种灵活的设备，为这些实验提供了独特的重要功能。GBS （Global Braginskii Solver）是一种全3D全局减少漂移的Braginskii解算器，以前曾用于线性和环面器件的建模，将用于模拟这些实验。实验模型的比较将在广泛的条件下进行，从相干到完全发展的湍流状态。

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.