A wedgelet current system on Saturn

Magnetic energy and mass release processes are key issues to understand the magnetospheric dynamics and aurorae processes on planets. Recent studies reveal that rotationally driven processes at dayside on giant planets are much more important than we ever expected. The discovery on the dayside magnetodisc reconnection demonstrates that the rotation effect can overcome the solar wind compression to sufficiently stretch magnetic field lines at dayside (Guo et al., 2018, doi: 10.1038/s41550-018-0461-9). A long-standing small-scale reconnection process was also shown at all local times (Guo et al., 2019, doi: 10.3847/2041-8213/ab4429). Using Cassini in situ multiple instruments data, we here proposed a wedgelet current system governing the entire magnetosphere of Saturn, which can explain the observational phenomena of quasi-periodical electron energization recurrence and beads-like structure in the main aurora region. Localized active regions with finite azimuthal lengths in the magnetosphere were discretely and azimuthally distributed along the magnetodisc and rotated with the magnetosphere. The electron energizations recurred at the spacecraft are related to each active region that passed by. These studies reveal that the dynamics in magnetodisc are global effects on giant planets, which are not always restrained at nightside.