Nonlinear periodic and solitary structure generated by the coupling of drift and electron-acoustic waves in an inhomogeneous and field-aligned shear flow plasma

The study used a magnetized, inhomogeneous, collisionless, two-temperature electron plasma with shear flow parallel to the ambient magnetic field B=B0ẑ to investigate nonlinear periodic (cnoidal) wave structures created by the coupled drift wave (DW) and electron-acoustic wave (EAW). Satellite observations in auroral regions, the plasma sheet boundary layer, Earth's magnetosphere, and solar wind, as well as laboratory experiments, have identified coexisting hot and cold electron populations. As these electron populations have different temperatures, they are categorized as hot and cold electrons. The hot electrons follow Kappa distribution, while the positive ions stay stationary in the background, and cold electrons have a temperature lower than the hot electrons, i.e., Tc<Th. It is also noted that the superthermality and temperature ratio of hot to cold electrons have an influence on the linear phase speed of the waves. By considering co-moving transformation, a nonlinear partial differential equation is obtained, which ensures the formation of cnoidal waves and solitons under certain boundary conditions in a specific region. The demonstration of the effects of significant modifications occurring due to the density inhomogeneity on cnoidal and solitary structure profiles of the pure drift mode is a noteworthy mark of the investigation. The frequency of the coupled EAW and DW is estimated to be ∼150 Hz, which is in accordance with the observations. The parameters involved have significant impact on the amplitude and width of the solitons. Figures are plotted to show how the amplitude and width of the soliton decrease with the increase in shear flow parameter Sc, cold to hot electron temperature ratio σc=Tc/Th, and cold ion drift speed vcn∗. Moreover, how the amplitude and width of the soliton increase with the increase superthermality index κh. The appropriate plasma parameters of broadband electrostatic noise in the ionosphere's dayside auroral zone are used. The highlighting feature of this study is the formation of cnoidal waves due to drift waves and impacts of variation of shear flow on their profiles.