The Contribution of Radiation Pressure to the Stability of a Standard thin Keplerian Accretion Disk around a Neutron Star with Axisymmetric Magnetic Field Dipole

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Addis Ababa University


In this thesis, we have studied the dynamic properties of an accretion disk formed from the in ow of plasma from a blotted out companion star. The disk extends from an inner radius of 106m ( RA Alfeven radius) to 100RA (see gure 1.4). We have divided the disk into three regions: an outer region dominated by gas pressure and free-free opacity, a middle region dominated by gas pressure and electron scattering, and an inner region dominated by radiation pressure and electron scattering. We have also derived the radiation pressures and gas pressure in the inner region of the disk as a function of "r" using radial dependence of the central temperature and the density. The latter was obtained using the basic equations for thin accretion in non-relativistic case . Analyses of the instability of the disk is made between RA and 10RA (RA < r < 10RA) based on the instability condition ( o > 3=5). This is occurred at high temperature, at which the opacity is dominated by electron scattering and radiation pressure is strong



Axisymmetric Magnetic Field Dipole