On the flux jumps in hard superconductors

The paper is devoted to the investigation of critical state stability against flux jumps in hard superconductors accounting for the critical current density dependence on the temperature and magnetic field. A flat sample with finite thickness is considered. The stability criteria were found for the Kim-Anderson critical state model as well as for the region close to the upper critical field Hc2. It was shown that the stability diminishes near Hc2. The stability conditions were found for the total range of external fields below Hc2. It was found that under certain conditions the magnetic instabilities may develop in two isolated regions of the external fields. (author)