Tidal Force and Torque on the Crust of Neutron Star
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Date
2013-06
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Addis Ababa University
Abstract
A neutron star core super
uid rotates at a di erent rate to that of the crust, while spinning
down at the same steady-state rate as the rest of the star, because of the assumed pinning
between the super
uid vortices and the inner crust. We nd that the magnitude of this
rotational lag changes with time and also depends on the distance from the rotation axis;
the core super
uid supports an evolving pattern of di erential rotation. We predicted
change of the lag might occur as discrete events which could result in a sudden rise of the
spin frequency of the crust of a neutron star, as is observed in glitches in radio pulsars.
Glitches are believed to have been caused by break aways of pinned vortices.This new
possibility for the triggering cause of glitches in radio pulsars is further supported by an
estimate of the total predicted excess angular momentum reservoir of the core super
uid.
The model seems to o er resolutions for some other aspects of the observational data on
glitches. The goal of this project is to show the tidal force e ect on the di erential motion
of the crust with respect to the core of the neutron star could lead to the reduction of
glitch frequencies and eventually produced gravitational locking between the core and the
crust of a neutron star
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Keywords
The Crust of Neutron Star