Because of the intense radiation in the Jovian system, some sort of shielding must protect any humans that might try to live on Jupiter's moons. Living underground would be a must, but people could not stay down forever -- and the facilities would need to be constructed in the first place. Instead of direct shielding, one efficient way to do this on Jupiter's cold moons would be to use high-temperature superconducting magnets. Although the ~130 Kelvin level there is rather hot for existing high-Tc superconductors, some prototype magnets have been made with critical temperatures approaching this level. Large superconducting rings of this material could create magnetic fields which would not stop the incoming radiation, but rather deflect incoming charged particles around certain inhabited regions on the surface. (This would not work for x-rays and other uncharged particles).