Effects of Non-Maxwellian Particle Distributions on Ion-Acoustic Waves in a Magnetized Cometary-Like Multi-Ion Plasma

Abstract

This study investigates nonlinear ion-acoustic waves (IAWs) in a magnetized multi-ion plasma motivated by cometary plasma environments, where hydrogen ions, oxygen ions, and non-Maxwellian electron populations may coexist due to solar-wind interaction and particle acceleration processes. The distribution is adopted here as an effective model for electrons with superthermal tails, rather than as a universal description of all cometary electron populations. Two scenarios are analyzed: (1) oxygen ions follow Cairns–Tsallis distributions (CTD) while hydrogen ions behave as isothermal fluids, and (2) hydrogen ions adopt CTD while oxygen ions are governed by fluid dynamics. Using 3D fluid equations, reductive perturbation theory (RPT) and samll \(k\) perturbation expansion, we derive Zakharov–Kuznetsov (ZK) equations to describe nonlinear IAWs and their three-dimensional instability (TMI). Results reveal that wave features-such as phase speed, amplitude, width and instability growth rates depend critically on nonthermal electron parameter, nonextensivity, magnetic field orientation and basic plasma parameters. Notably, instability arises when specific threshold conditions are met, with growth rates sensitive to wave propagation angles. These findings deepen our understanding of wave dynamics in cometary and other space plasmas with non-Maxwellian components.