Effects of nonthermal electrons and ion beams on ion-acoustic double layers in warm ion plasma
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ORIGINAL PAPER
Effects of nonthermal electrons and ion beams on ion-acoustic double layers in warm ion plasma I Paul1, A Chatterjee2 and S N Paul1,2* 1
Department of Physics, Jadavpur University, Kolkata 700032, India
2
East Kolkata Centre for Science Education and Research, P-1, B. P. Township, Kolkata 700 094, India Received: 06 October 2019 / Accepted: 20 July 2020
Abstract: The effects of nonthermal electrons and ion beams on the ion acoustic double layers in warm ion plasma have been studied using the pseudopotential technique. Sagdeev potential of ion-acoustic wave in the plasma has been derived and the solution of ion acoustic double layers has been obtained. The critical value of nonthermal parameter of electrons for existence of double layers is obtained and discussed. The profiles of double layers in the plasma are drawn taking different values of density and temperature of ion beams, and the nonthermal parameter of electrons obeying the critical condition. It has been shown that both compressive and rarefactive double layers are excited in the plasma depending on the values of nonthermal electrons and ion beam parameters. The width of double layers is also graphically discussed. The results are new and may be useful in understanding the acceleration processes of charged particles in space plasma. Keywords: Ion acoustic wave; Nonthermal electron; Ion beam; Sagdeev potential; Double layers
1. Introduction In recent years, there is a great deal of interest on the study of nonlinear propagation of waves in plasma consisting of electron/ion beams because of its importance in understanding the nonlinear electrostatic disturbances in magnetosphere and solar plasma [1, 2]. The nonlinear structure of plasma is changed considerably in presence of electron/ ion beams. Krivoruchku et al. [3] have shown that an electron beam in plasma can change the propagation of the Trivelpiece-Gould solitons. Later, it is shown by Gell et al. [4] that compressive solitary waves are excited in an electron beam plasma system. However, the effects of ion beams are also important to excite the ion acoustic solitary waves (IASWs) in plasma. Abrol and Tagare [5] have obtained a modified Koteweg-deVries (KdV) equation for IASWs in presence of ion beams in plasma composed of cold ions, beam ions and nonisothermal electrons. They have critically discussed the effect of resonant electrons, trapped and free electrons, plasma-ion to beam-ion mass ratio and beam-ion concentration on the amplitude and
*Corresponding author, E-mail: [email protected]; [email protected]
width of IASWs. Later, Karmakar et al. [6] have obtained the solution of IASWs in ion-beam plasma with multipleelectron-temperatures through the derivation of a modified KdV equation. It is seen that the existence solitons and its behaviour depends effectively on the ion beam as well as on the multiple electron temperatures. The solitons might be large amplitude with the addition of a small percentage of ion-beam concentration or by the increase of electrontemperatur
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