Alfven Wave Collisions: The Fundamental Building Block of Plasma Turbulence

Alfv\'en 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 Alfv\'en waves traveling in opposite directions along the magnetic field. Therefore it is these interactions, often referred to simply as ``collisions'' between counter-propagating Alfv\'en 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 Alfv\'en wave collisions. We describe here a fundamental study of the properties of these Alfv\'en wave collisions both in the MHD and kinetic Alfv\'en wave regimes, employing both asymptotic analytical solutions of the nonlinear interaction between counter-propagating Alfv\'en waves and supporting gyrokinetic numerical simulations. Intuition from these studies is exploited to support planned laboratory experiments to measure the nonlinear evolution of Alfv\'en wave collisions on the Large Plasma Device (LAPD) at UCLA.