Alfvenic perturbations with finite Larmor radius effect in non-Maxwellian electron–positron–ion plasmas

Abstract

Linear and nonlinear coupled kinetic Alfven acoustic (CKAA) waves in low-β electron–positron–ion (e-p-i) plasmas are investigated in this paper, and the main focus is on highlighting the role of non-thermal electrons and positrons that follow the generalized (r, q) distribution. In this regard, a linear dispersion relation is derived, and the effect of positron concentration and (r, q) distributed electrons and positrons is explored. Nonlinear analysis is performed by using the Sagdeev potential approach and two-potential theory. The results are compared with those of the previous studies of CKAA waves in e-p-i plasmas where electrons and positrons follow Maxwellian and kappa distributions. An important feature of our study is the observation of the existence of density dip solitons for spiky distribution. It is shown that the inclusion of positrons alters the existence regimes of the solitary structures, and, interestingly, the behavior of soliton propagation is different in the two existence regimes for increasing or decreasing concentration of positrons. Most importantly, it is shown that the spatial scales over which solitons form in e-p-i plasmas are shorter than the ones that form in e-i plasmas for compressive solitary structures. Interestingly, the situation is reversed for rarefactive solitary structures. The present study is beneficial in comprehending the linear and nonlinear propagation of CKAA waves in plasmas where positrons are present, and there is a simultaneous presence of nonthermal features in the observed distribution functions.