Basic Laboratory Experiments of Plasma Turbulence: Alfven Wave Collisions

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The dynamics and evolution of turbulence in a magnetized plasma is a fundamental issue in plasma science. An improved basic understanding of this fundamental plasma physics process will impact many research areas and disciplines in which plasma turbulence plays an important role: in astrophysical plasmas from clusters of galaxies to accretion disks around black holes to the birthplace of stars in the turbulent interstellar medium of our Galaxy; in space plasmas such as the solar corona, solar wind, and Earth's magnetosphere; and in the laboratory plasmas of the magnetic confinement fusion program. Cross-cutting studies to advance our knowledge of plasma turbulence, therefore, have the potential to impact this very wide range of research frontiers.Alfven waves play a central role in the dynamics of magnetized plasma turbulence. Theoretical studies suggest that the nonlinear interactions that constitute the turbulence occur only between Alfven waves traveling in opposite directions along the magnetic field. Therefore it is these interactions, often referred to simply as "collisions" between counter-propagating Alfven waves, that form the fundamental building blocks of plasma turbulence. Today's modern theories of anisotropic magnetized plasma turbulence have been developed based on this intuitive concept of counter-propagating Alfven wave collisions. To better understand the nonlinear dynamics of these Alfven wave collisions---and to test this central concept underpinning modern theoretical models of plasma turbulence---observational or experimental measurements of Alfven wave collisions are essential. This project seeks to improve our understanding of the fundamental building blocks of plasma turbulence by performing laboratory experiments on the Large Plasma Device (LAPD) at UCLA to measure the nonlinear evolution of Alfven wave collisions, with theoretical guidance provided by nonlinear kinetic simulations of Alfven wave collisions using the Astrophysical Gyrokinetics code, AstroGK.