Abstract
Investigation of positive and negative dust charge fluctuations on the propagation of dust-ion acoustic waves (DIAWs) in a weakly inhomogeneous, collisionless, unmagnetized dusty plasmas consisting of cold positive ions, stationary positively and negatively charged dust particles and isothermal electrons. The reductive perturbation method is employed to reduce the basic set of fluid equations to the variable coefficients Korteweg-de Varies (KdV) equation. At the critical ion density, the KdV equation is not appropriate for describing the system. Hence, a new set of stretched coordinates is considered to derive the modified variable coefficients KdV equation. It is found that the presence of positively charged dust grains does not only significantly modify the basic properties of solitary structure, but also changes the polarity of the solitary profiles. In the vicinity of the critical ion density, neither KdV nor the modified KdV equation is appropriate for describing the DIAWs. Therefore, a further modified KdV equation is derived, which admits both soliton and double layer solutions. (C) 2008 American Institute of Physics.