Theoretical study of laser-excited Mach cones in dusty plasmas

A two-dimensional hydrodynamic model for a monolayer of dust particles is used to study the Mach cones excited by a moving laser beam through dusty plasmas. Numerical results for the density perturbation and the velocity distribution of dust particles exhibit both compressional and shear-wave Mach cones. It is found that the compressional Mach cones exist in cases of both supersonic and subsonic excitations, and that they consist of multiple lateral or transverse wakes. On the other hand, realization of single shear-wave Mach cones depends closely on the excitation technique, the laser scanning speed, and the discharge pressures. It is found that, when the scanning direction of the laser beam is perpendicular to the laser force, a transition from multiple compressional Mach cones to a single shear Mach cone can be achieved either by lowering the scanning speed or by increasing the discharge pressures.