Excitation of cylindrical and spherical precursor solitons in a flowing dusty plasma: Experimental and simulation studies

Abstract

We report the first laboratory observation of precursor cylindrical and spherical solitons excited in a flowing dusty plasma. The experiments are carried out in an inverted Π-shaped dusty plasma experimental device in which a dust cloud is created in a background Argon plasma using micrometer-sized Kaolin particles. Using the single gas injection technique, the dust fluid is made to flow in a controlled manner over a cylindrical (or a spherical) charged object for a range of flow velocities. When the flow velocity exceeds a critical value, cylindrical (or spherical) solitons are excited, which, in the frame of the dust fluid, travel in the upstream direction, while wake structures propagate in the downstream direction. Unlike one-dimensional solitons, the amplitudes of these higher dimensional solitons decrease with time (and hence distance) while maintaining constancy of the product of their amplitudes with the square of their widths. The spherical solitons decay at a rate faster than the cylindrical soliton. It is also found that their amplitudes and velocities increase, and their widths decrease with an increase in the dust fluid velocity. Furthermore, the radii of curvature of the cylindrical and spherical solitons decrease with an increase in the dust fluid flow velocity. A 3D molecular dynamics simulation of the excitation phenomenon provides a good theoretical support to the experimental observations.