Abstract: Jupiter and Saturn’s internal magnetic fields carve out a cavity in the solar wind (and its embedded interplanetary magnetic field) to form two of the largest magnetospheres in our solar system. Their locations in the heliosphere are characterized by vastly different solar wind conditions than are available at Earth, thus affording, for example, the exploration of some of the highest Mach number shocks ever recorded in situ.

In addition to their external interactions with the solar wind, they have geologically active moons continuously loading plasmas into their magnetospheres: Io’s volcanoes at Jupiter and Enceladus’ geysers at Saturn. These internally sourced plasmas interact with the surrounding planetary magnetic fields, giving rise to mechanisms that ultimately control the magnetospheres’ states and drive their dynamics. Furthermore, our evolving understanding of Saturn’s rings is revealing their influence in this context as well.

In 2016, NASA’s Juno spacecraft undertook the first polar orbit of Jupiter, and in 2017, NASA/ESA’s Cassini spacecraft performed its final orbit, which were highly inclined and adjusted to pass through the gap between Saturn’s atmosphere and innermost ring; both providing unprecedented coverage and proximity to their planets. These highly inclined, proximal orbits enable the spacecraft to directly sample the ionospheres and traverse magnetic field lines threading the auroral regions, as well as those connecting the planets to their active moons and ring systems (for Saturn, at least). Such measurements are essential to understanding coupling processes and establishing the big picture of these planetary systems operate on a global scale. Altogether, these place Jupiter and Saturn each in unique points in the parameter landscape of both solar wind and satellite interactions with planetary magnetospheres. I will highlight recent observations that provide a new view of the gas giants and underline them, to our current understanding, as the most dynamic and diverse environments in our solar system.