Re: Jupiter's magnetic fields
jupiter most likely has some kind of core which consists of heavier-than-atmosphere materials, perhaps all squished up into a high pressure ball, and the pressure might cause 'molten core' kinds of activity. Iron and Nickel (because of the lowest binding energy per nucleon) is common in the universe, and probably exists on every planet and celestial object in at least some amount. That being said, it might also be the same reason why the sun has a magnetic field
Jupiter emits radio frequencies and as such could have some level of plasma activity (like the sun) that could be the source of its magnetic field.
Or it could be a combination of factors like these [and other things not considered yet]
/me expects Jupter's core to have a lot of diamond crystals in it, like Uranus.