Vortex lines and field reversal in anisotropic superconductors

In an anisotropic superconductor, a vortex line which is not parallel to a symmetry axis can have surprising features in its magnetic field pattern. In this paper we examine one such feature, the reversal of the component of the magnetic field parallel to the vortex axis. This field reversal leads to an attractive interaction between two parallel lines, when their positions satisfy certain criteria. Using perturbation theory, we develop simple analytic results which allow us to identify the supercurrents responsible for the magnetic field pattern. The importance of different screening lengths is stressed.