CORRELATED CREEP RATE OF A VORTEX LINE UNDER THE EFFECT OF VORTEX TENSION AND ITS RELATION TO THE GLITCHES OF PULSARS

In our earlier works, we have calculated the correlated creep velocity of a vortex line with line tension, which is pinned to a perfect simple-cubic lattice, and creeps out under the action of a biased potential by thermal activation. In this paper, we extend the result to cases in which the biased potential, the line tension, and the pinning energy of the line are all functions of position. Although an evaluation of the exact correlated creep velocity is difficult, a good approximate form can be found. We show that the Anderson-Kim thermal-activation formula in the vortex-creep model is still valid after suitable modification even though their uncorrelated-creeping assumption is incorrect. We apply our formalism to study the motion of vortex lines in the crustal region of neutron stars. The model results suggests that the steady-state configuration of vortex lines should form a set of hyperbolic-like curves because the stronger-pinning regions (which also have higher tension) are located in the inner regions of the crust. Perturbations, like a star quake, can cause a large number of vortex lines to unpin from the stronger-pinning region and the tension forces the vortex lines to move by a macroscopic distance. Such a mechanism may be responsible for the glitches of pulsars.