Flux spiral instability in a transport current carrying type‐II superconductor

The nucleation of vortex flux lines on a surface of a transport current carrying type II superconductor in the presence of an external magnetic field H e occurs at H e ˜ H cl , the first critical field. A spiral flux line in a long cylinder and in a long thin ellipsoid is investigated. In the latter case the force‐free magnetic fields are also considered.