Effect of q-nonextensive hot electrons on bifurcations of nonlinear and supernonlinear ion-acoustic periodic waves

The review summarises recent theoretical achievements and observational manifestations of a new, recently discovered type of nonlinear oscillations in multi-component plasmas, namely super-nonlinear periodic waves and super-nonlinear solitary waves (supersolitons). Both are characterised by a non-trivial topology of their phase portraits, highly anharmonic profile shapes, extremely long periods, and large amplitudes. Based upon multi-fluid magnetohydrodynamic plasma models, examples of ion-acoustic and Alfven super-nonlinear waves are considered. A multi-component nature of the plasma was revealed to be a crucial condition for the existence of these super-nonlinear waves, with the complexity of the system growing with the number of plasma species accounted for in the model. A minimum number of plasma components which allow for the existence of super-nonlinear waves are also discussed. From the observational point of view, typical signatures of periodic super-nonlinear waves are manifested, for example, in the oscillatory processes operating in the magnetised plasma of the solar corona and ground-based plasma machines. Super-nonlinear solitary structures (supersolitons) of an electrostatic origin are recognised in the Earth’s magnetosphere, laboratory experiments with chemically active plasmas, and numerical simulations.

Above the weak nonlinearity: super-nonlinear waves in astrophysical and laboratory plasmas

Electrostatic solitary waves (ESWs) have been observed in the Earth's magnetosphere, solar wind, lunar wake, and also in other planetary magnetospheres. The observed characteristics of the ESWs have been interpreted in terms of models based either on Bernstein-Green-Kruskal (BGK) modes/phase space holes or ion- and electron-acoustic solitons. However, the space community has favored the models based on BGK modes/phase space holes. In this review, current understanding of the fluid models for ion-and electron-acoustic solitons and double layers in multi-component plasmas is presented. The relationship between the theoretical models and space observations of ESWs is emphasized. Two specific applications of ion- and electron-acoustic solitons to the occurrence of weak double layers and coherent electrostatic waves in the solar wind and the lunar wake are discussed by comparing the observations and theoretical predictions. It is concluded that models based on ion- and electron-acoustic solitons/double layers provide a plausible interpretation for the ESWs observed in space plasmas.

A review of nonlinear fluid models for ion-and electron-acoustic solitons and double layers: Application to weak double layers and electrostatic solitary waves in the solar wind and the lunar wake

Abstract Propagation of nonlinear and supernonlinear positron-acoustic periodic waves is examined in an electron-positron-ion plasma composed of static positive ions, mobile cold positrons, and q-nonextensive electrons and hot positrons. Employing the phase plane theory of planar dynamical systems, all qualitatively different phase portraits that include nonlinear positron-acoustic homoclinic orbit, nonlinear positron-acoustic periodic orbit, supernonlinear positron-acoustic homoclinic orbit, and supernonlinear positron-acoustic periodic orbit are demonstrated subjected to the parameters q,μ1,μ2,σ1,σ2$q,{\\mu_{1}},{\\mu_{2}},{\\sigma_{1}},{\\sigma_{2}}$, and V. The nonlinear and supernonlinear positron-acoustic periodic wave solutions are reported for different situations through numerical computations. It is observed that the nonextensive parameter (q) acts as a controlling parameter in the dynamic motion of nonlinear and supernonlinear positron-acoustic periodic waves. The dynamic motions for the positron-acoustic traveling waves with the influence of an extrinsic periodic force are investigated through distinct qualitative approaches, such as phase portrait analysis, sensitivity analysis, time series analysis, and Poincaré section. The results of this paper may be applicable in understanding nonlinear, supernonlinear positron-acoustic periodic waves, and their chaotic motion in space plasma environments.

Dynamical Behavior of Supernonlinear Positron-Acoustic Periodic Waves and Chaos in Nonextensive Electron-Positron-Ion Plasmas

“Supersolitons,” the structures associated with the stationary solitary solutions with the Mach number greater than those associated with the double layers, were introduced in 2012. Later, many researchers have reported the existence domain of the supersolitons in different plasma constituents. However, their evolutionary dynamical behavior and stability were main concerns and were not yet explored. We performed fluid simulation of ion acoustic supersolitons in a plasma containing two-temperature electrons having kappa distributions in the presence of cold fluid ions. Our simulation shows that a specific form of the initial perturbation in the equilibrium electron and ion densities can evolve into ion acoustic supersolitons, which maintain their shape and size during their propagation. This is first-ever simulation to confirm the stability of the supersolitons that opens a new era in the field of solitary wave structures in space and laboratory plasmas.

First-ever model simulation of the new subclass of solitons “Supersolitons” in plasma

The effect of excess superthermal electrons is investigated on finite amplitude nonlinear ion-acoustic waves in a magnetized auroral plasma. The plasma model consists of a cold ion fluid, Boltzmann distribution of cool electrons, and kappa distributed hot electron species. The model predicts the evolution of negative potential solitons and supersolitons at subsonic Mach numbers region, whereas, in the case of Cairn's nonthermal distribution model for the hot electron species studied earlier, they can exist both in the subsonic and supersonic Mach number regimes. For the dayside auroral parameters, the model generates the super-acoustic electric field amplitude, speed, width, and pulse duration of about 18 mV/m, 25.4 km/s, 663 m, and 26 ms, respectively, which is in the range of the Viking spacecraft measurements.

O. R. Rufai

Papers

Effect of excess superthermal hot electrons on finite amplitude ion-acoustic solitons and supersolitons in a magnetized auroral plasma

Obliquely propagating ion-acoustic solitons and supersolitons in four-component auroral plasmas