There are several sources of heat on Jupiter but the one being studied by this mission is the result of the very large magnetic field around Jupiter's generatin

There are several sources of heat on Jupiter but the one being studied by this mission is the result of the very large magnetic field around Jupiter's generating auroras that are several times larger than the diameter of Earth. [edit] Original statement wasn't completely accurate, as it does study the auroras, but they are generated by the planet itself. The solar wind doesn't reach the atmosphere of Jupiter.