Nonlinear theory of backward and oblique ion-acoustic waves in plasma with unidirectionally moving ions

Oblique ion-acoustic waves in plasma with unidirectionally moving ions are considered. Within the framework of the linear theory, a two-dimensional dispersion relation is derived and the occurrence of backward and sideward waves in the system is demonstrated. The nonlinear theory of backward and sideward waves developed in this study is based on derivation and analysis of Sagdeev’s pseudopotential. The nonlinear profiles of backward and sideward ion-acoustic waves were calculated. It was found that backward and sideward waves are undistinguishable in their profiles from a regular forward ion-acoustic wave.