Nonlinear theory of ion-acoustic waves in an electron-positron-ion plasma
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MA OSCILLATIONS AND WAVES
Nonlinear Theory of Ion-Acoustic Waves in an Electron–Positron–Ion Plasma A. E. Dubinov and M. A. Sazonkin Sarov State Physical and Technical Institute, ul. Dukhova 6, Sarov, Nizhni Novgorod oblast, 607186 Russia Received May 4, 2008
Abstract—An analytical nonlinear gasdynamic theory of ion-acoustic waves in an e–p–i plasma is developed for the case in which all the plasma components in the wave undergo polytropic compression and rarefaction. An exact solution to the basic equations is found and analyzed by the Bernoulli pseudopotential method. The parameter range in which periodic waves can propagate and the range in which solitary waves (solitons) exist are determined. It is shown that the propagation velocity of a solitary is always higher than the linear ion sound velocity. The profiles of all the physical quantities in both subsonic and supersonic waves are calculated. The results obtained agree well with both the data from other papers and particular limiting cases. PACS numbers: 52.27.Ep, 52.35.Fp DOI: 10.1134/S1063780X09010024
1. INTRODUCTION
Na22 source [18] were injected into a Penning trap and were confined there for a long time, thereby producing a quasineutral e–p plasma. However, it is not excluded that the beam electrons with energies of ~10 eV may generate a certain number of positive ions in the residual gas, thereby creating e–p–i-plasma. Of course, in all the above examples, the energy and composition of the positively charged plasma components differ significantly. Therefore, in some cases, there is an electron–ion plasma with a positron admixture, whereas in other cases, this is an electron–positron plasma with an ion admixture. Over the last several years, there have appeared a great number of theoretical papers devoted to various collective processes in e–p–i plasma (see, e.g., [19– 32]), such as Alfvén [19–21], drift [22, 23], and magnetoacoustic waves [24]; double layers [25]; and phase holes [26]. In [27–32], various aspects of the propagation of electromagnetic waves in e–p–i plasmas were analyzed, in particular, the Faraday rotation of the polarization plane [30] and the formation of relativistic electromagnetic envelope solitons [31] and electromagnetic vortices [32]. In [33], modulational interaction of electromagnetic waves with electron sound was considered. In the present paper, we study specific features of nonlinear ion-acoustic waves in e−p–i-plasma. Previously, this type of wave was investigated in [34–47]. Thus, in [34], the nonlinear theory of ion-acoustic waves in plasma with cold ions and inertialess isothermal electrons and positrons was developed using the Sagdeev pseudopotential method and the conditions were determined under which stationary ion-acoustic solitons can exist. A similar problem was considered in [35] using the method of expansion in a power series in
An electron–positron–ion (e–p–i) plasma with positive ions is rather widespread in nature. Such a plasma can occur, e.g., in the inner region of accretion discs in the vicinity of b
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