Self-heating and ac losses in superconductors

Self-heating induced by ac loss in superconductors under different thermal boundary conditions has been investigated numerically. Self-heating effect results in non-uniform distributions of temperature and critical current density in superconductors. The self-heating effect is also sensitive to the thermal boundary conditions. A low-field instability of the critical current density is found when the external magnetic field decreases to near zero after fully penetrating the superconductors, leading to low-field flux jumps as observed in MgB2 and YBa2Cu3O7 superconductors