Structure of Ion Acoustic Solitons and Shock Waves in a Two-Component Plasma

Time-independent solitary waves and shocks are investigated in a two-component plasma using a fluid model and kinetic theory. It is found that very small concentrations of a light ion can drastically alter the structure, changing the potential maximum φm by an order of magnitude. For a fixed Mach number, a critical density ratio of light to heavy ions is found at which φm changes discontinuously from a value large enough to reflect the light ions to one which allows them to traverse the shock front and enter the downstream flow. The downstream oscillatory structure normally seen in a shock is completely quenched by dissipation due to light ion reflection at concentrations of 3-8% He in an Ar plasma for typical Te/Ti and Mach number values.