  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 ~ 4 MeV is required to form a kink at
densities of ~ 3.4 x 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.
