The title, basically. If we're at a temperature below the critical temperature (let's just say for a Type 1 superconductor) and an applied magnetic field less than the critical magnetic field, it will be in the superconducting state. But if we increase the field beyond the critical point, it will go into the normal state. So if we set the temperature well below ##T_c## and made the applied field right below ##H_c##, it seems like we could oscillate ##H## to make it go in and out of the superconducting state. Is this the case, first of all? Second, if that's not somehow impossible, I imagine there must be some sort of upper limit to the frequency you could do this at. You can get pretty damn fast magnetic field oscillations. Will the superconductor switches states back and forth that fast?