Effect of Pressure Anisotropy on Nonlinear Periodic Waves in a Magnetized Superthermal Electron-Positron-Ion Plasma

The propagation properties of electrostatic cnoidal waves (periodic waves) and solitons are studied in a magnetized electron-positron-ion (EPI) plasma bearing ion pressure anisotropy and superthermality. In a two-dimensional geometry, we considered the ions to be warm having pressure anisotropy due to magnetic field. The anisotropic ions are modeled via double adiabatic Chew-Golberger-Low (CGL) theory and the lighter species (electron and positron) are following kappa distributions. A Korteweg-de Vries (KdV)-type equation is derived by employing reductive perturbation technique, and obtained the nonlinear periodic waves solutions with appropriate boundary conditions. The anisotropy in the ion thermal pressure relative to the external magnetic field (different values in parallel and perpendicular directions) have significant effects on the characteristics of cnoidal waves. It is observed that by increasing the ion parallel and perpendicular pressure (keeping the relative anisotropy) tends to reduce the wavelength of the cnoidal wave structure, while the amplitude tends to increase. The influence of superthermality of electron and positron, the positron content and strength of the external magnetic field on the cnoidal waves are studied in detail. Furthermore, phase portrait analysis is carried out and traced out the equilibrium points around which nonlinear periodic waves can be formed. The saddle points which correspond to the homoclinic orbits are also shown. The investigation can be useful in exploring the nonlinear wave dynamics in both laboratory and space plasma where ion pressure anisotropy and superthermality exist.