Dr. Gabby Provan, a planetary researcher in the School of Physics and Astronomy, joined the MIST team (Magnetosphere, Ionosphere and Solar-Terrestrial) to discuss the latest findings from Jupiter and Saturn.
The gas giants Jupiter and Saturn are both rapid rotators, with active volcanic moons and complicated ring systems. Their magnetospheres are driven both by external drivers (e.g. the upstream solar wind and interplanetary magnetic field), planetary rotation and internal plasma sources. For both planets the internally-produced plasma is centrifugally unstable, it diffuses away from the planet and starts to sub co-rotate as it moves into the middle magnetosphere. Large-scale field-aligned current systems are generated in regions of flow shear between different plasma regimes, coupling the planetary magnetosphere-ionosphere systems. At the University of Leicester we model these field-aligned current, with the models also including consideration of the magnetodisc currents. In this talk, I will introduce this modelling work in the context of the Jovian system, and compare its predictions of field-aligned currents with observations from the Juno spacecraft and the Hubble space telescope. We will also produce a comprehensive report of the field-aligned currents observed at Saturn by the Cassini spacecraft, including during Cassini’s Grand Finale where currents were observed on field lines mapping to Saturn’s rings. For the Saturnian system we will discuss how these currents are related to the ubiquitous planetary period oscillations. For both planets we will consider the modulation of field-aligned currents by the solar wind and the interplanetary magnetic field. We will finish by detailing some of the outstanding questions in the field.