Dust ion acoustic solitary structures in presence of nonthermal electrons and isothermal positrons

Abstract

The Sagdeev potential technique has been employed to study the dust ion acoustic solitary waves and double layers in an unmagnetized collisionless dusty plasma consisting of negatively charged static dust grains, adiabatic warm ions, and isothermally distributed electrons and positrons. A computational scheme has been developed to draw the qualitatively different compositional parameter spaces or solution spaces showing the nature of existence of different solitary structures with respect to any parameter of the present plasma system. The qualitatively distinct solution spaces give the overall scenario regarding the existence of different solitary structures. The present system supports both positive and negative potential double layers. The negative potential double layer always restricts the occurrence of negative potential solitary waves, i.e., any sequence of negative potential solitary waves having monotonically increasing amplitude converges to a negative potential double layer. However, there exists a parameter regime for which the positive potential double layer is unable to restrict the occurrence of positive potential solitary waves. As a result, in this region of the parameter space, there exist solitary waves after the formation of positive potential double layer, i.e., positive potential supersolitons have been observed. But the amplitudes of these supersolitons are bounded. A general theory for the existence of bounded supersolitons has been discussed analytically by imposing the restrictions on the Mach number. For any small value of positron concentration, there is no effect of very hot positrons on the dust ion acoustic solitary structures. The qualitatively different solution spaces are capable of producing new results for the formation of solitary structures.