Numerical investigation of magnetic reconnection in Jupiter’s dayside magnetodisc

Context. Dayside magnetodisc reconnection is a unique process that may occur in rapidly rotating magnetospheres with internal plasma sources, and it is not expected at Earth. Several observations suggest that dayside magnetodisc reconnection could be driven in the Kronian magnetosphere. This raises the question as to whether it can occur at Jupiter, the fastest rotating planet in the Solar System. Recent reports have suggested its occurrence, but the limited number of identified events leaves the overall global picture in the Jovian magnetosphere uncertain. Aims. The primary objective of this study is to answer whether dayside magnetodisc reconnection could exist within the Jovian magnetosphere through the use of global magnetohydrodynamics (MHD) simulations. Additionally, we aim to conduct a numerical investigation to reveal its general distribution for possible future exploration. Methods. The numerical simulations for Jovian magnetospheric dynamics are based on three-dimensional MHD calculations, which enable magnetic reconnection through numerical resistivity. In post-processing procedures, the simulated magnetodisc reconnection event is primarily identified by equatorial Bθ reversals, accompanied by an analysis of local plasma flows and global magnetic field lines. Results. Our global MHD simulations reveal the existence of magnetodisc reconnection within the dayside Jovian magnetosphere. The simulation results indicate that dayside magnetodisc reconnection is more likely to occur during solar wind rarefaction, primarily due to the rapid expansion of the dayside magnetospheric volume. This expansion allows a rotation-driven centrifugal force to generate sufficient magnetic field line stretching for current sheet thinning and reconnection. In simulated dayside events, Bθ reversals may occur locally or non-locally through rotational transport from reconnection sites at earlier magnetic local times. Conclusions. The existence and the features derived from simulations are testable as Galileo/Juno has accumulated a considerable amount of dayside magnetospheric data. These results are valuable for future Jovian missions, such as JUICE and Europa Clipper, and provide new insights into interpreting measurements from other rapidly rotating systems.