Soliton propagation in a moving electron-positron pair plasma having negatively charged dust grains

Abstract

We consider an electron-positron pair plasma that has negatively charged dust grains. Being the same mass of the electrons and positrons, both of these species contribute to the wave excitation in the plasma. Since the frequency of oscillations is high, the dust grains are considered to be fixed and they only provide the restoring force for the wave excitation. For the sake of completeness, we include the finite temperatures of the electrons and positrons species and derive the expressions for the phase velocities. Two types of modes propagating in opposite directions occur in this pair plasma model. Based on Korteweg-de Vries (KdV) equation, it is realized that these modes evolve only into compressive solitons. However, usual KdV approach fails when both the species carry the same temperatures and also drift with the same velocity. Under this situation, modified KdV (mKdV) equation is derived that shows the occurrence of rarefactive solitons also, which carry the same amplitudes as the compressive solitons attain corresponding to mKdV equation. In addition to the expressions of peak amplitude and width of the solitons, we calculate soliton energy for examining their propagation characteristics in detail under the effect of positron to electron temperature ratio σ, their drift velocities (ve0 and vp0), dust concentration nd0, and dust charge valency Zd. The issue of nonvanishing coefficient of nonlinearity is also discussed in greater detail.