‘‘Standing’’ diffusion of electromagnetic fields in superconductors with gradual resistive transitions

Electromagnetic field diffusion in superconductors with gradual resistive transitions may exhibit a peculiar ~anomalous! mode which does not exist in superconductors with sharp ~ideal! resistive transitions. This is a ‘‘standing’’ mode. In the case of this mode, the electromagnetic field on a superconductor boundary increases with time, while the region occupied by the electromagnetic field within the superconductor does not expand. In this paper, an exact analytical solution to the appropriate nonlinear diffusion equation is derived. It is demonstrated that this solution can be physically interpreted as the standing mode. The standing mode solution is also obtained by using a ‘‘rectangular profile’’ approximation and these two results are compared. © 1996 American Institute of Physics. @S0021-8979~96!03508-1#