Applied Physics Seminar: “Exploring Novel Properties of Strongly Magnetized Plasma”

Abstract:
Many useful properties of plasmas stem from their ability to be controlled by magnetic fields. As such, modeling the transport of particles, momentum and energy in magnetized plasmas is a central topic of plasma theory. An often-underappreciated assumption of plasma theory is that it assumes the plasma is weakly magnetized in the sense that the gyrofrequency of particles is much smaller than the plasma frequency. Here, we use first-principles molecular dynamics simulations and new theoretical methods to explore the properties of strongly magnetized plasmas. A few novel behaviors have been uncovered. One is that the friction force on a test ion moving through a strongly magnetized plasma shifts to obtain components that act perpendicular to its velocity. These components cause qualitative changes to the average trajectory of the ion, such as changing its gyroradius and gyrofrequency in non-intuitive ways. They also translate to qualitative changes in macroscopic material properties of the plasma, such as the electrical conductivity, viscosity, and energy relaxation rates. Simulations also reveal that strong magnetization causes long-range correlations between particles and can cause onset of strongly coupled (liquid-like) properties at plasma density and temperature conditions that are normally expected to be in a weakly coupled (gas-like) state. Although strongly magnetized plasmas are not the norm, they do arise in several contexts, including non-neutral plasmas in antimatter traps, high magnetic field approaches to fusion energy, and in dense astrophysical objects such as magnetars. These results suggest that unexpected behaviors may arise in these systems, and it motivates potential application that may make use of these properties.