I= LINEAR AND NONLINEAR DYNAMICS OF NONUNIFORN ELECTRON €“ POSITRON €“ ION PLASMAS
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Title of Thesis
LINEAR AND NONLINEAR DYNAMICS OF NONUNIFORN ELECTRON €“ POSITRON €“ ION PLASMAS

Author(s)
Qamar €“ Ul - Haque
Institute/University/Department Details
Comsats Institute of Information Technology (CIIT), Islamabad, Pakistan
Session
2007
Subject
Physics
Number of Pages
98
Keywords (Extracted from title, table of contents and abstract of thesis)
linear dynamics, nonlinear dynamics, ion plasmas, vortices, coupled acoustic, electromagnetic drift, electron €“ positron €“ ion plasmas, nonlinear coherent structures

Abstract
The dynamics of low frequency electrostatic and electromagnetic drift waves in collisionless nonuniform magnetized electron-positron-ion (e-p-i) plasmas is studied. It is found that the drift wave frequency can be very low in such plasmas depending upon the concentration of different plasma species. The Hasegawa-Mima equation is modified. The solutions of the nonlinear equations are obtained in the form of vortices in both electrostatic and electromagnetic limits.

The two dimensional large amplitude ion acoustic waves can give rise to dipolar vortex structures in magnetized homogeneous e-p-i plasmas as well. It is shown that in nonuniform plasmas the acoustic mode can couple with electrostatic drift waves and vortex-like nonlinear structures can be produced.

A set of nonlinear equations is derived which describe the coupling of ion acoustic wave, Alfven wave and drift wave. These equations also give the stationary solution in the form of dipolar vortices. Linear dispersion relation of several coupled electrostatic and electromagnetic low frequency modes is also obtained.

Linear and nonlinear Alfven waves are also studied in the presence of a background current gradient in e-p-i plasmas. The instability criterion becomes dependent upon the concentration of different species in a three component plasma.

It is also pointed out that the drift waves can become unstable due to shear flow produced by externally applied electric field. The modified Rayleigh instability condition is obtained which is applicable to both electron-ion and e-p-i plasmas. It is proposed that the shear flow driven drift waves can be responsible for large amplitude electrostatic fluctuations in tokamak edges. A particular form of the shear flow can give rise to counter rotating vortices and vortex chains. A comparison of this work with the limiting cases of electron-ion and electron positron plasmas is also presented. It is pointed out that this investigation can be applicable to both astrophysical and laboratory plasmas.

Download Full Thesis
5086.56 KB
S. No. Chapter Title of the Chapters Page Size (KB)
1 0 Contents
412.3 KB
2 1 Introduction 5
707.31 KB
  1.1 Linear And Nonlinear Dynamics Of Nonuniforn Electron €“ Positron €“ Ion Plasmas 5
  1.2 Nonlinear Coherent Structures 5
  1.3 Layout Of The Thesis 12
3 2 Brief Overview Of The Vortices 13
1317.43 KB
  2.1 What Are Vortices 13
  2.2 Types Of Vortices 25
4 3 Linear And Nonlinear Drift Waves In E-P-I Plasmas 36
585.35 KB
  3.1 Introduction 36
  3.2 Set Of Equations 38
  3.3 Linear Dispersion Relation 38
  3.4 Drift Wave Dipolar Vortices 41
  3.5 Electrostatic Limit 44
  3.6 Conclusions 46
5 4 Coupled Acoustic And Drift Waves In E-P-E Plasmas 47
707.42 KB
  4.1 Acoustic And Electrostatic Drift Waves 47
  4.2 Electromagnetic Drift And Acoustic Waves 52
  4.3 Conclusions 60
6 5 Current Gradient And Shear Flow Driven Vortices And Instabilities 61
1012 KB
  5.1 Basic Concept Of Instability 61
  5.2 Drift Alfven Vortices With Current Gradient 62
  5.3 Counter Rotating Vortices 71
  5.4 Conclusion 77
7 6 Summary 81
203.83 KB
8 7 References 84
263.24 KB