Global fully kinetic simulations of Mercury’s magnetosphere: a virtual spacecraft approach for BepiColombo orbital phase

We present here synthetic BepiColombo observations of Mercury’s magnetosphere obtained from two global fully kinetic particle-in-cell simulations performed with the iPIC3D code under two interplanetary magnetic field (IMF) configurations: a southward IMF and one along the average Parker-spiral direction at Mercury. Electromagnetic fields and particle bulk measurements and energy distributions are sampled self-consistently along four Mio case study orbital trajectories using a virtual spacecraft approach, providing a synthetic characterization of the plasma environment expected during the orbital phase of the mission. The simulated observations reproduce the sequence of solar wind, magnetosheath, and magnetospheric regions encountered along each orbit and reveal signatures of magnetotail reconnection near closest approach, including enhanced field-aligned electron flows and associated suprathermal particle populations. Comparison of the dawn and dusk flank trajectories underlines asymmetries between the two regions, including evidence of enhanced plasma density on the dusk side and differences in magnetosheath extent that depend on the IMF orientation. We further investigate temperature-anisotropy-driven instabilities along the trajectories. Ion mirror mode and Alfvén/ion-cyclotron instabilities are found to occur systematically within the magnetosheath, whereas electron whistler and electron firehose conditions are preferentially reached near closest approach and in localized magnetosheath intervals. We also examine the role of IMF orientation in shaping the plasma stability properties along the trajectories. The reconstructed particle energy spectra and electromagnetic fluctuations provide additional diagnostics of trapped populations and kinetic processes associated with magnetotail activity. Overall, these results establish a physically consistent reference framework for the interpretation of BepiColombo observations during the forthcoming orbital phase at Mercury.