Global hybrid-particle modelling of Mercury’s space plasma environment and BepiColombo observations

We present a study of Mercury’s space weather using our global 3D open source hybrid-particle modelling platform, RHybrid (paRallel Hybrid). The model resolves the kinetic motion of ions via the Lorentz force and the fluid dynamics of charge-neutralising electrons through Ohm’s law, self-consistently coupled with the evolution of the magnetic field via Faraday’s law. Efficient parallelisation for high-performance computing enables the code to resolve spatial structures and ion velocity distributions with high resolution. Mercury’s surface is modelled as a particle-absorbing inner boundary, while the crust–mantle region is represented as a resistive spherical shell atop an ideally conducting core. The planetary magnetic field is modelled as a dipole offset northward from the planet’s centre. Here, the RHybrid model is applied to simulate the interaction between the Hermean magnetosphere and the solar wind under selected upstream solar wind and interplanetary magnetic field conditions. We focus on the BepiColombo mission’s swingbys of Mercury and the interpretation of in situ observations, including the properties and boundaries of charged particles, the magnetic field, and plasma waves in the Hermean plasma environment.

• Jarvinen R., Alho M., Kallio E., Pulkkinen T.I. (2020), Ultra-low frequency waves in the ion foreshock of Mercury: A global hybrid modeling study, Mon. Notices Royal Astron. Soc., 491, 3, 4147-4161, doi:10.1093/mnras/stz3257
• Kallio E., Jarvinen R., Massetti S., Alberti T., Milillo A., Orsini S., De Angelis E., Laky G., Slavin J., Raines J.M., Pulkkinen T.I. (2022), Ultra-low frequency waves in the Hermean magnetosphere: On the role of the morphology of the magnetic field and the foreshock, Geophys. Res. Lett. 49, 24, doi:10.1029/2022GL101850
• RHybrid repository: https://github.com/fmihpc/rhybrid