You're right, other moons should be receiving their dose of Jupiter's fields. Here are some pictures of Io and Europa. I'm not sure these are updated, the article is a bit old
http://www.holoscience.com/news/jupiter.htm
There was an article about a binary that was interacting through their plasma's, I'll look for it. 'Meantime have fun with the Europa pictures, they are quite special.
Cheers.