A half century of Io plasma torus science: current mysteries and opportunities

The Io plasma torus was first observed 50 years ago and has been studied by all of the space missions to visit Jupiter, the JAXA Hisaki satellite, HST, and a host of ground-based observatories.  These observations reveal significant structure in the torus: the "ribbon" near Io's orbit; the "warm torus," outside of the ribbon; and the "cold torus" inside of the ribbon.  Individually, the ribbon, cold torus, and warm torus have been the subject of significant study, but to date, no study has focused on combining the observations of these disparate parts of the torus.  I will outline several scientific questions that can be answered by simple analysis of existing and planned long-term observations of the torus.  The answers to these questions are important because they can help focus the efforts of Earth-based remote-sensing observations that would support JUICE, Europa Clipper and Tiawen-4 studies of the Jovian magnetosphere and Galilean satellites.