Pinning of superfluid vortices is predicted to prevail throughout much of a neutron star .
Based on the idea of Alpar et al. , I develop a description of the coupling between the solid and liquid components of a neutron star through thermally-activated vortex slippage , and calculate the the response to a spin glitch .
The treatment begins with a derivation of the vortex velocity from the vorticity equations of motion .
The activation energy for vortex slippage is obtained from a detailed study of the mechanics and energetics of vortex motion .
I show that the “ linear creep ” regime introduced by Alpar et al .
and invoked in fits to post-glitch response is not realized for physically reasonable parameters , a conclusion that strongly constrains the physics of post-glitch response through thermal activation .
Moreover , a regime of “ superweak pinning ” , crucial to the theory of Alpar et al .
and its extensions , is probably precluded by thermal fluctuations .
The theory given here has a robust conclusion that can be tested by observations : for a glitch in spin rate of magnitude \Delta \nu , pinning introduces a delay in the post-glitch response time .
The delay time is t _ { d } = 7 ( t _ { sd } / 10 ^ { 4 } \mbox { yr } ) ( ( \Delta \nu / \nu ) / 10 ^ { -6 } ) d where t _ { sd } is the spin-down age ; t _ { d } is typically weeks for the Vela pulsar and months in older pulsars , and is independent of the details of vortex pinning .
Post-glitch response through thermal activation can not occur more quickly than this timescale .
Quicker components of post-glitch response as have been observed in some pulsars , notably , the Vela pulsar , can not be due to thermally-activated vortex motion but must represent a different process , such as drag on vortices in regions where there is no pinning .
I also derive the mutual friction force for a pinned superfluid at finite temperature for use in other studies of neutron star hydrodynamics .