Preliminary measurements of phase coupling in the dust acoustic wave

Bispectral analysis is a powerful tool for studying nonlinear phenomena and is applied here to the dust acoustic wave. In particular, we examine three situations: (1) the naturally occuring wave mode, (2) the wave mode subject to an external modulation at a single drive frequency, and (3) the wave mode subject to an external modulation at two drive frequencies. Nonlinear interactions are observed in each of these cases. When an external modulation at a single drive frequency is applied, a threshold condition is observed for nonlinear interactions to result in three-wave coupling and the excitation of a third mode. In the case of an external modulation at two-drive frequencies, significant nonlinear wave mixing is observed. Taken together, these measurements demonstrate that the dust acoustic wave is an excellent system for studying nonlinear interactions and three-wave coupling.