Large amplitude slow ion-acoustic solitons, supersolitons, and double layers in a warm negative ion plasma with superthermal electrons

The pseudopotential approach is used to investigate the ion thermal and electron superthermal effects on the slow mode solitary wave propagation characteristics in a negative ion plasma, comprising warm positive and negative ions and kappa-distributed electrons. The Sagdeev pseudopotential for the plasma model is derived and analyzed in a systematic way. While it is well known that a negative ion plasma supports the propagation of the fast mode normal solitons, it is found that it supports, in addition to the slow mode normal solitons, the propagation of the slow mode supersolitons and double layers for high values of the negative ion density. The double layers occur as the lower limit to the supersoliton existence range and as the limiting factor for the propagation of normal solitons. When the relative temperature of the two ion species decreases, it is found that the Mach number range supporting the propagation of the nonlinear structures reduces, while the amplitudes of solitons and supersolitons decrease, and these effects are enhanced by the superthermal behavior of the electrons. The amplitudes of the double layers increase with a decrease in the relative temperature of the two ion species but decrease with an increase in the electron superthermality.