Analytical model of the response of a superconducting film to line   currents
  We theoretically investigate the response of a superconducting film to line currents flowing in linear wires placed above the film, and we present analytic expressions for the magnetic-field and current distributions based on the critical state model. The behavior of the superconducting film is characterized by the sheet-current density $K_z$, whose magnitude cannot exceed the critical value $j_cd$, where $j_c$ is the critical current density and $d$ is the thickness of the film. When the transport current $I_0$ flowing in the wire is small enough, $|K_z|$ is smaller than $j_cd$ and the magnetic field is shielded below the film. When $I_0$ exceeds a threshold value $I_{c0}\propto j_cd$, on the other hand, $|K_z|$ reaches $j_cd$ and the magnetic field penetrates below the film. We also calculate the ac response of the film when an ac transport current flows in the linear wires. 
Yasunori Mawatari and John R. Clem