Modelling Superfluid Dynamics in Neutron Stars

Neutron stars are the collapsed cores of massive stars that have undergone a supernova explosion. They are the densest known astrophysical object, with a mass typically 1.4 times that of the Sun but compressed into a radius of approximately 10 km. Observations reveal that neutron stars have extremely diverse ranges of spin periods and magnetic field strengths. They also have revealed many remarkable properties, including rotational "glitches," which are an instantaneous increase in the observed rotation rate. However, the neutron star's magnetic field evolution and interior composition, and the role these play in producing phenomena such as glitches, are poorly understood. Deep within the star, where the density exceeds the nuclear equilibrium density, neutrons and protons both become superfluid. As a result, the star's rotation and magnetic flux become quantised into extremely thin vortices and fluxtubes. Large-scale observable phenomena, like the timescale for magnetic evolution in the star's core, depend crucially on microscale superfluid dynamics; but current theoretical models are hampered by an incomplete understanding of the interactions between superfluid vortices, fluxtubes and crustal nuclei. My thesis aims to improve our theoretical understanding of neutron star dynamics and evolution, model and describe the interaction between vortices and magnetic flux tubes in the neutron star core using a flux rope model of the magnetic field, and to model and describe the phenomenon of glitches observed in pulsars.