In this paper propagation of the nonlinear cnoidal ion-acoustic waves in unmagnetized electron-positron-ion plasma have been studied. The nonextensivity distribution function was used to describe the plasma electrons and positrons, while plasma ions are taken high relativistic.We have used the reductive perturbation method (RPM) to study the characteristic of ionacoustic cnoidal waves in this three-component plasma. The Korteweg-de Vries equation, which describes the nonlinear waves in such plasma, has been derived. In this work, we have investigated the effects of relativistic ions and q-nonextensive distribution of electrons and positrons on the characteristics of the ionacoustic periodic (cnoidal) wave, such as the amplitude, wavelength, and frequency. Manuscript profile

In this paper, considering the importance of ion acoustic waves in nonlinear phenomena of plasma, the combined effects of nonextensivity and nonthermality parameters on the ion acoustic cnoidal nonlinear waves studied. In this regard, the hybrid Cairns-Tsallis distribution function used to describe the electrons and positrons. Conditions of formation of nonlinear ion acoustic waves and permissible values of nonextensivity (Q) and nonthermality (a) parameters were determined and the behavior of these waves with changes in these parameters in this type of plasma have been studied. For this purpose, we have used the reductive perturbation method (RPM) to derive the corresponding KdV equation for the ion acoustic wave, then considering the Sagdeev potential, the conditions for the generation of ion acoustic waves in the cnoidal and soliton form discussed. The effect of nonextensivity (Q) and nonthermality (a) parameters on the Sagdeev potential (potential well width and depth), wave amplitude and frequency investigated. The results show that for all of the acceptable values of Q and a the cnoidal ion acoustic wave is compressive. Manuscript profile