Nonlinear Alfv\'{e}n Wave Interactions on the Large Plasma Device

The nonlinear dynamics of large amplitude Alfv\'{e}n waves is believed to play a major role in the evolution of the macroscopic properties of numerous laboratory plasmas and astrophysical systems. However, despite their importance the nonlinear dynamics of these fluctuations remains point of great controversy with few prior thorough experimental measurements. Nonlinear interactions between Alfv\'{e}n waves are being studied in the Large Plasma Device (LAPD) at UCLA, using large amplitude, $\delta B / B_{0} \sim 1 \%$, waves generated by LaPD's Alfv\'{e}n wave MASER or by antennas. In these experiments, two large amplitude shear Alfv\'{e}n waves are launched at different frequencies and beat against one another. The subsequent nonlinear generation of density fluctuations at the beat frequency along with the formation of numerous discrete Alfv\'{e}nic sidebands has been observed using both wave launching mechanisms over a broad range of plasma parameters and launch wave frequencies. Such interactions resemble a form of parametric decay, namely the modulational instability. In particular the spatial and temporal characteristics as well as amplitude scaling of the interaction as evident by its effects on magnetic, density, and potential fluctuations will be presented.