Dynamics of Exotic Nuclear Rod Formation for the Origin of Neutron Star Glitches

The inner crust of a neutron star comprises lattices of neutron-rich nuclei and a neutron superfluid, in which many quantized vortex lines exist. The vortex lines are pinned by nuclei but can jump from one pinning site to another. In previous papers by Mochizuki & Izuyama and Mochizuki, Oyamatsu, & Izuyama, it was pointed out that such vortex lines may induce nuclear matter rods along the vortex cores. Such an exotic nuclear rod along a vortex line is formed by captures of nuclei from outside the vortex core and by subsequent fusion reactions of the captured nuclei with the nuclei inside the core. The nuclear rod was shown to have a lower energy than the original nuclear lattice. As the next step, dynamics for the rod formation is required. Namely, to conclude that the nuclear rods are actually formed in the neutron star, we need to confirm that the formation time of the nuclear rod is shorter than the time of the vortex sojourn at a pinning site. It is the purpose of this paper to confirm this. We find that under conditions appropriate to the Vela pulsar, the rod formation time is indeed much shorter than the vortex sojourn time in the frontier region (the region where a vortex line is tangential to the central core of the star). Rod formation is attained by pycnonuclear reactions rather than by thermonuclear ones. The resulting exotic nuclear rod formation in the frontier region can lead to a pulsar glitch, as proposed by Mochizuki & Izuyama. A brief summary of our microscopic glitch model is also presented.