Hybrid modeling of Mercury’s magnetosphere: Assessing accuracy in ion counting statistics

In this study, we present a method for comparing hybrid plasma simulations with spacecraft measurement data, with a focus on Mercury’s interaction with the solar wind. Utilizing the 3D global hybrid simulation model Adaptive Ion-Kinetic Electron-Fluid (AIKEF), we derived ion energy distributions in Mercury’s magnetosheath using different solar wind input scenarios. We introduce three concepts for counting the simulated particles and assess the systematic and stochastic variations. Furthermore, we evaluate the effect of different phase space resolutions within the model. We find that a lower phase space resolution influences the distribution peaks, thus emphasizing the need for adequate particle resolution. Dedicated simulation runs for BepiColombo’s second and third flyby maneuvers at Mercury, based on solar wind measurement data from the BepiColombo fluxgate magnetometer on board the Mio spacecraft (Mio-MGF) and Planetary Ion Camera (PICAM) instruments, enable quantitative comparison of simulated data with ion spectrometer measurements. The energy flux distributions measured by PICAM fall within the confidence intervals of the modeled data. Additionally, we find that systematic deviations dominate the stochastic deviations. Our analysis shows that our simulation is an effective tool for understanding magnetospheric conditions, and it can assist in interpreting the in situ spacecraft measurements from BepiColombo upon its arrival.