Nonlinear shear flow-modified dust ion acoustic waves

Abstract

Nonlinear equations for the modified dust ion acoustic waves are solved analytically in the small amplitude limit in a plasma having field-aligned shear flow of ions relative to electrons, while the heavy dust fluid is assumed to be stationary. Landau damping is negligibly small in this case because ion number density is larger than that of the electrons, and hence parallel phase speed of dust ion acoustic waves becomes greater than ion thermal speed. As a result, the non-resonant unstable electrostatic mode grows rapidly when the instability condition is satisfied. On the other hand in the nonlinear regime, the waves can produce dipolar vortices whose size will depend upon the scale size of the shear in the zero order flow velocity and density ratios of the species. Here, a general theoretical model is presented, which is applicable to dusty plasmas of planetary magnetospheres, comets, and inter-stellar clouds.