Existence and propagation characteristics of ion-acoustic Kadomtsev–Petviashvili (KP) solitons in nonthermal multi-ion plasmas with kappa distributed electrons

Abstract

The dynamics of two dimensional Kadomtsev–Petviashvili (KP) electrostatic solitary waves (ESWs) propagating in multi-ion unmagnetized plasma is investigated, in the presence of energetic (nonthermal) electrons. Two distinct ion components are considered as inertial fluids, while inertialess electrons are characterized by an excess superthermal population described by a kappa distribution. The primary (heavier and cold) ion population is assumed to be positively charged, while the charge and sign of the (lighter and warm) ions is left arbitrary in the model. A linear analysis reveals the existence of two harmonic modes propagating with different phase speeds, identified as slow and fast ion-acoustic waves i.e., SIAW, FIAW respectively. Nonlinear analysis, based on a multiscale (reductive perturbation) technique, leads to a two-dimensional Kadomtsev–Petviashvili (KP) equation for the electrostatic potential. Pulse-shaped electrostatic potential solitary wave solutions and associated bipolar electric field structures are obtained analytically as well numerically. A parametric investigation reveals that, if both ion species are positively charged, then either negative or positive polarity electrostatic potential solitary waves structures may occur for the slow (SIAW) mode case (only), depending on the light ion density and temperature. On the other hand, considering a negatively charged light (warm) ion fluid case, then solitary structures of SIAW are formed of positive polarity (only), while their fast counterpart FIAW is of opposite (negative) polarity. The (O, H) multi-ion plasma is considered and parametric dependence of nonlinear electrostatic solitary wave characteristics (amplitude, width) on the intrinsic plasma configurational parameters i.e., light-to-heavy ion density and light ion to electron temperature ratios and nonthermal electrons spectral index kappa is investigated.