Synchronization of the Dust Acoustic Wave in an RF and a DC Discharge Plasma

A spatiotemporal measurement of the synchronization of a self-excited dust acoustic wave with an external modulation in a radio frequency (RF) discharge plasma is presented. This synchronization process is then compared with the synchronization observed in a dc discharge plasma. In both discharge types, the wave becomes synchronous with an external modulation behind a propagating synchronization front that travels at a slower speed than the phase velocity of the wave and the speed of this synchronization front decreases with increasing neutral gas pressure. It is also observed that the degree of synchronization decreases with increasing nonlinearity in the wave and varies with the strength of the external modulation. Finally, it was observed that the entire wave volume is observed to be synchronous with the external modulation with the smaller clouds observed in the dc discharge, while only a subvolume of the wave is observed to be synchronous with the external modulation in the larger clouds observed in an RF discharge.