Shock structure in collisional positive ion - negative ion plasmas

Abstract The weakly nonlinear dynamics of low-frequency sound waves are studied in a positive ion - negative ion (PINI) plasma with the aim of investigating the strong collisional effect on its propagation characteristics. The nonlinear wave dynamics is shown to be governed by a Kakutani-Kawahara equation in the strong collisional limit. In contrast to the electron-ion plasmas, the temperature and inertial effects of both the ions significantly modify the nonlinearity and the dispersion of the wave. Analytical solution together with numerical simulations show that a soliton (localized pulse) first collapses into a weak noise shelf and then form shock like structures. The relevance and potential application of the results in future numerical simulation and experimental studies of laboratory and space PINI plasmas are also discussed.