  The rotating neutron superfluid in the inner crust of a neutron star is
threaded by quantized vortex lines. The pinning force from lattice nuclei and
the Magnus force from neutron superfluid act onto a vortex line that has a
finite tension. The configuration of a vortex line in equilibrium comprises a
number of pinned straight lengths separated by unpinned kinks when the rotation
axis is slightly inclined to the major axis of a crystal lattice and the Magnus
force is not so strong. Energy of $\sim 4 {MeV}$ is required to form a kink at
densities of $\sim 3.4 \times 10^{13}{g cm}^{-3}$. Magnus force makes the
vortex line parabolic on global scale. There exist two modes, rotational and
helical (Kelvin), for oscillations allowed on a vortex line. The vortex
oscillations in the pinned straight segments are possible only above a minimum
frequency. We find no unstable mode that grows with time. Hence, the vortex
configurations with kinks may be stable and yield the strongly pinned state.
The essence of our results may not be altered even when we consider the vortex
behaviors in a polycrystalline structure. Our studies suggest that pinning of a
vortex line in a polycrystalline structure would be still strong enough to
explain the large glitches.
