The gasdynamic approach in the nonlinear theory of electrostatic waves in symmetric plasma

A nonlinear theory of electrostatic waves in symmetric plasma is constructed using the gasdynamic (adiabatic) description of dynamics of plasma components, as well as the Sagdeev pseudopotential method. The possibility of existence of stationary solitary electrostatic waves of both polarities of potential is demonstrated; in so doing, the sufficient condition of this is the absence of equilibrium between plasma components or the inequality of their adiabatic exponents. The boundaries are determined of the region in the parameter space, in which solitary waves are possible, as well as their limiting velocities. The profiles of basic physical quantities in the wave are calculated.