FLUCTUATIONS OF FLUX LINES ON THE SURFACE OF SUPERCONDUCTOR

In this paper, we study the magnetic structure of the half-ring flux line ended on the surface of a superconductor. The elemental modes for these half-ring flux lines are the half-ellipse flux lines ended on and perpendicular to the surface. The statistics of these half-ring flux lines is, in a certain degree, similar to the vortex-antivortex pairs in thin superconducting films. An abrupt change of the thermodynamic properties for this system takes place at a temperature lower than T_c. It is analogous to the KT transition in thin superconducting films in certain sense.