A new class of solitary waves—supernonlinear solitons (supersolitons)—the phase trajectories of which envelop one or several inner separatrices on the wave phase portrait has been revealed. It is shown that supersolitons of the ion-acoustic type can exist in an unmagnetized plasma that contains no less than four kinds of charged particles. The conditions for the existence of supersolitons are specified. The profile of the electrostatic potential in an ion-acoustic supersoliton is determined. It is shown that a supersoliton can be easily recognized experimentally among conventional solitons by using a differentiating circuit in the measuring channel.

Ion-acoustic supersolitons in plasma

We report properties of ion acoustic freak waves that propagate in a plasma composed of warm ions and ultrarelativistic electrons and positrons. The dynamics of the nonlinear freak waves is governed by the nonlinear Schrodinger equation. The possible region for the freak waves to exist is defined precisely for typical parameters of white dwarfs and magnetars corona. It is found that for low wave number, the nonlinear ion-acoustic wave packets are structurally stable in magnetars corona than in white dwarfs. However, for large wave numbers the situation is opposite. The critical wave number threshold (kc), which indicates where the modulational instability sets in, is defined for both applications. It is seen that near to kc the freak wave amplitude becomes high, but it decreases whenever we stepped away from kc. For the wave numbers close to kc, the increase of the unperturbed density ratio of positrons-to-electrons (β) would lead to increase the freak wave amplitude, but for larger wave numbers the ampli...

Freak waves in white dwarfs and magnetars

The stability of modulation of ion-acoustic waves in a collisionless electron–positron–ion plasma with warm adiabatic ions is studied. Using the Krylov–Bogoliubov–Mitropolosky (KBM) perturbation technique a nonlinear Schrodinger equation governing the slow modulation of the wave amplitude is derived for the system. It is found that for given set of parameters having finite ion temperature ratio (T
 i
 /T
 e
 ) the waves are unstable for the values of k lying in the range k
 min<k<k
 max. On increasing the ion temperature ratio (T
 i
 /T
 e
 ), it is found that k
 min and k
 max, both decreases and product PQ increases. The range of unstable region shifts towards the small wave number k, as temperature ratio (T
 i
 /T
 e
 ) increases. The positron concentration and temperature ratio of positron to electron, change the unstable region slightly. As positron concentration increases both k
 min and k
 max for modulational instability increases and maximum value of the product PQ shifts towards the larger value of k.

https://link.springer.com/content/pdf/10.1007%2Fs10509-013-1520-4.pdf

Modulational instability of ion-acoustic waves in electron–positron–ion plasmas

Arbitrary amplitude ion-acoustic solitary waves propagating in a magnetized plasma composed of positive ions, superthermal electrons and positrons are investigated. For this purpose, the ions are represented by the hydrodynamical fluid equations while the non-Maxwellian electrons and positrons densities are assumed to follow kappa (κ) distribution. The basic equations are reduced to a pseudoenergy-balance equation. Existence conditions for large amplitude solitary waves are presented. The analytical and numerical analysis of the latter show that the ion-acoustic solitary wave can propagate only in the subsonic region in our plasma system and it is significantly influenced by the plasma parameters. The present analysis could be helpful for understanding the nonlinear ion-acoustic solitary waves propagating in interstellar medium and pulsar wind, which contain an excess of superthermal particles.

Arbitrary amplitude ion-acoustic solitary waves in superthermal electron-positron-ion magnetoplasma

The nonlinear properties of fast magnetosonic solitary waves in a quantum degenerate electron-positron (e-p) plasma in the presence of stationary ions for neutralizing the plasma background of bounded cylindrical geometry were studied. By employing the standard reductive perturbation technique and the quantum hydrodynamic model for the e-p fluid, the cylindrical Kadomtsev-Petviashvili (CKP) equation was derived for small, but finite, amplitude waves and was given the solitary wave solution for the parameters relevant to dense astrophysical objects such as white dwarf stars. By a suitable coordinate transformation, the CKP equation can be solved analytically. An analytical solution for magnetosonic solitons and periodic waves is presented. The numerical results reveal that the Bohm potential has a main effect on the periodic and solitary wave structures. By increasing the values of the plasma parameters, the amplitude of the solitary wave will be increased. The present study may be helpful in the understan...

Cylindrical fast magnetosonic solitary waves in quantum degenerate electron-positron-ion plasma

Solutions in the form of cylindrical magnetosonic solitons of compression and rarefaction were obtained within the scope of the three-species electromagnetic gas-dynamic model of an electron-positron-ion plasma. These solutions can describe formation of cylindrical structures in accretion disks and jets in the vicinity of compact astrophysical objects.

https://www.tpbin.com/Uploads/Subjects/3cddedf8-6fc5-4443-bd83-f6cc300740dd.pdf

V. K. Valiulina

Papers

Magnetosonic cylindrical soliton in electron-positron-ion plasma