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Title of Thesis

Babur M. Mirza
Institute/University/Department Details
Department of Mathematics/ Quaid-i-Azam University Islamabad
Number of Pages
Keywords (Extracted from title, table of contents and abstract of thesis)
compact star, gravitomagnetic effects, compact astrophysical sources, plasma, compact stellar source, magnetohydrodynamic fluid

The gravitomagnetic effects on a plasma surrounding an isolated slowly rotating compact star are studied. The star is assumed to be a degenerate homogeneous highly conducting plasma. Regarding the plasma as an axially symmetric highly conducting magnetohydrodynamic fluid, the electromagnetic field of the star is determined by obtaining exact solutions to the generalized Maxwell equations for a non-rotating and a slowly rotating compact gravitational source. It is found that slow rotation and hence the gravitomagnetic effects do not modify or reduce the electromagnetic field of the compact star. Hence the field remains the same as for a non-rotating compact object. The solution for the electromagnetic field is then used to discuss the plasma accretion dynamics in vicinity of a compact star endowed with an electromagnetic as well as gravitation field. The gravitomagnetic effects are found to directly influence the accretion of the plasma surrounding the star. Numerical studies show that the electric as well as gravitomagnetic forces oppose the plasma in-fall, whereas the magnetic and the gravitomagnetic forces contribute to the in-fall.

In the second part of the thesis the effects of gravitomagnetic field on plasma oscillations in compact star crustal region, formed of a solid state plasma (mostly 56Fe and other heavy elements such as Si, O, C, and He ions and a gas of free electrons) are studied. With bound ions in the crust as a fixed background, electrons exhibit relatively free oscillations. It is found that as a result of the gravitomagnetic force the collective electron oscillations are coupled to the rotational frequency of the star. The gravitomagnetic force thus lowers the plasma frequency, and depending on the mass, radius and rotational frequency of the star, reduces the frequency of the electromagnetic waves transmitted through the stellar crust.

Download Full Thesis
8381.95 KB
S. No. Chapter Title of the Chapters Page Size (KB)
1 0 Contents
779.93 KB
2 1 Introduction 7
1171.22 KB
  1.1 Preamble 7
  1.2 Observational Basis Of Compact Astrophysical Sources 8
  1.3 Plasma In Compact Stars 10
  1.4 Gravitoelectromagnetism And The Measurement Of Lens- Thirring Effect 11
  1.5 Outline Of The Thesis 13
3 2 Astrophysics Of Compact Stars 15
2452.03 KB
  2.1 Introduction 15
  2.2 The Gravitational Field Of A Compact Stellar Source 16
  2.3 Hydrostatic Equilibrium For A Compact Star 23
  2.4 Limiting Mass, Radius, And Angular Velocity Of A Compact Star 26
  2.5 Matter Arrangement In A Compact Star 35
  2.6 Electrical Neutrality Of A Compact Star 37
  2.7 Compact Star Plasma Atmosphere 40
4 3 The Electromagnetic Field Due To A Slowly Rotating Compact Star 1 43
2008.26 KB
  3.1 Introduction 43
  3.2 Electromagnetic Field Tensor For An Ideal Magnetohydrodynamic Fluid 45
  3.3 Stationary Observers And Zamos 49
  3.4 Calculation Of The Electromagnetic Field Components In A Zamo 51
  3.5 General Relativistic Maxwell Equations 53
  3.6 Electromagnetic Field Due To A Compact Star 57
  3.7 Discussion Of The Solutions Obtained By Separation Of Variable Technique 62
  3.8 Comments On Dipole (Multipole) Expansion 62
5 4 Plasma Accretion In Graviteletromagnetic Field 2 66
1613.12 KB
  4.1 Introduction 66
  4.2 The Gravitoelectromagnetic Approximation 68
  4.3 Charge Accretion In Gravitoelectromagnetic Approximation 74
  4.4 Numerical Solutions 77
  4.5 Discussion And Conclusions 83
6 5 Plasma Oscillations 3 85
1150.05 KB
  5.1 Introduction 85
  5.2 Plasma Frequency Shift For Electron Oscillations 87
  5.3 Collective Plasma Oscillations In Compact Star Crustal Regions 88
  5.4 Plasma Frequency Shift And Refractive Index 91
  5.5 Observational Detection Of The Gravitomagnetic Effects In Compact Star 92
7 6 Conclusions And Suggestions 98
889.81 KB
  6.1 A Gravitational Field Equations 100
  6.2 B Gravitational Units 103