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

University Of New Mexico, Albuquerque NM

Investigators

Abstract

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.