Modelling of Purely Advective Flows onto a Neutron Star

Kasar, Deep Gopinath (2025) Modelling of Purely Advective Flows onto a Neutron Star. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS Dissertation of Deep Gopinath Kasar (20MS128)) 20MS128_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (1MB)

Abstract

Due to the di↵erence in the rotational frequencies of the matter in the accretion disk and the Neutron star, the matter must adjust itself to rotate close to the star’s angular momentum, which is usually of a sub-keplerian nature. Prior studies on sub-keplerian flow onto a Black Hole have been ongoing since the 1990s. The present thesis work aims to extend this to Neutron stars by modelling purely advective flow falling on the magnetosphere of the Neutron star. The key di↵erence between the Black Hole and the Neutron star is the inner boundary condition, which changes the dynamics near the surface of the Neutron star and Black Hole. We use the HLLD Riemann Solver to model the ideal Magneto-hydrodynamic conditions around the Neutron star. Our simulations show the bending of matter by the magnetic field of the NS and changes in magnetic structure due to high ram pressure. We propose a modified plasma beta, which includes ram pressure to parametrize the purely advective flow.

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