ELECTROSTATIC AND ELECTROMAGNETIC SOLITONS IN MULTI-COMPONENT PLASMAS

Shahzad, Mahmood (2007) ELECTROSTATIC AND ELECTROMAGNETIC SOLITONS IN MULTI-COMPONENT PLASMAS. Doctoral thesis, Comsats Institute of Information Technology (CIIT), Islamabad.

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Abstract

The linear and nonlinear behavior of several low frequency electrostatic and electromagnetic waves in multi-component plasmas is investigated. Sagdeev potential approach has been used to obtain nonlinear solutions of the set of partial differential equations in the form of solitary pulses in many different astrophysical, space and laboratory multi-component plasmas. The ion acoustic solitary wave in a homogeneous magnetized electron-positron-ion (epi) plasma has been studied. It is found that the amplitude of ion acoustic solitary structure increases with the increase in percentage presence of positrons in a magnetized epi plasma, which shows the opposite behavior in comparison with the unmagnetized epi case already reported in literature. The ion acoustic solitary structures in magnetized epi plasmas are formed in subsonic region while in unmagnetized case the solitary structures are supersonic. The nonlinear kinetic Alfven wave (KA W) and slow shear Alfven wave (SSA W) have also been investigated in a homogeneous epi plasma. The electron density humps are formed in sub Alfvenic region for kinetic Alfven wave, which has the similar behavior as in the case of electron-ion (ei) plasma. However, the presence of positrons in ei plasma reduces the wave amplitude and width of the structure. The nonlinear slow shear Alfven wave in epi plasma has also been studied. It is found that the electron density dips are formed in super Alfvenic region for slow shear Alfven wave, which has the same behavior as in the case of ei plasma. In this case also the presence of positrons in the ei plasma reduces the wave amplitude and width of the nonlinear structure. The nonlinear ion acoustic wave in the presence of hot ions precipitation with electric field parallel to external magnetic field has been investigated in upper ionospheric region using fluid model. It is found that two different ion acoustic waves with different speeds can propagate in such a multi-component plasma. The electron density humps are formed in supersonic region. The presence of hot ions in an ei plasma plays destructive role in the formation of solitary structures. However, it is found that the wave amplitude increases if the mass of the hot ions is larger than the mass of the cold ions. The estimates for the electric field magnitude and the amplitude of density humps turn out to be (~100mV/m) and (15-20)% respectively, within the nonlinear structures are in good agreement with the Freja satellite observations.

Item Type: Thesis (Doctoral)
Uncontrolled Keywords: solitons, multi-component plasmas, electromagnetic waves, electrostatic waves, ion acoustic solitary structure, ion acoustic solitary wave, ion acoustic soliton
Subjects: Q Science > QC Physics
Depositing User: Muhammad Khan Khan
Date Deposited: 07 Nov 2016 04:34
Last Modified: 07 Nov 2016 04:34
URI: http://eprints.hec.gov.pk/id/eprint/3116

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