Nonlinear interactions between shear Alfv\'{e}n waves in a laboratory plasma*

Electromagnetic turbulence is thought to play an important role in plasmas in astrophysical settings (e.g. the interstellar medium, accretion disks) and in the laboratory (e.g. transport in magnetic fusion devices). From a weak turbulence point of view, nonlinear interactions between shear Alfv\'{e}n waves are fundamental to the turbulent energy cascade in magnetic turbulence. An experimental investigation of nonlinear interactions between shear Alfv\'{e}n waves in the Large Plasma Device (LAPD) will be presented. Two Alfv\'{e}n waves, generated by a resonant cavity, are observed to beat together, driving a low frequency perturbation at the beat frequency. The low frequency perturbation then scatters the Alfv\'{e}n waves, generating a series of sidebands. The observed interaction is very strong, with the normalized amplitude of the driven low frequency mode comparable to the normalized magnetic field amplitude ($\delta B/B$) of the interacting Alfv\'{e}n waves. Experimental details of this interaction will be presented along with other phenomena associated with large amplitude Alfv\'{e}n waves in LAPD, including electron heating and background density modification. Initial results from counter-propagating wave interaction experiments will also be discussed. \newline \newline In collaboration with Brian Brugman, Dept. of Physics and Astronomy and Center for Multiscale Plasma Dynamics, UCLA.