Daniel Teubenbacher

Mercury's environment is populated with a tenuous exosphere consisting mostly of sodium. After ionization by solar radiation, these sodium ions take peculiar paths through the magnetosphere; being trapped along dipolar magnetic field lines, re-impacting on the surface, or being lost downstream.Using the global 3D hybrid model AIKEF, we will investigate the effect of different interplanetary magnetic field (IMF) directions onto the ion's pathways through the magnetosphere. These model cases are then compared to BepiColombo plasma observations made along the swingbys 12346, aiding the magnetometer observations in the determination of the upstream IMF direction cases.

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.

The BepiColombo mission provides a unique opportunity to study Mercury’s magnetosphere, exosphere, and their interactions with the solar wind. The sixth Mercury flyby (MSB6) on January 8, 2025, offers a high-latitude trajectory potentially crossing through the plasma sheet and other key magnetospheric regions, making it a critical target for investigation. The aim of this study is to provide a model-based reference for ion and magnetic field measurements during MSB6 and to explore how solar wind and interplanetary magnetic field (IMF) conditions affect ion dynamics along the spacecraft trajectory. These results serve as a framework for interpreting BepiColombo’s observations, offering valuable insights that support the mission's scientific objectives. The global 3D hybrid plasma code AIKEF is employed to model Mercury’s magnetosphere under twelve scenarios, varying solar wind and IMF conditions. The model incorporates a kinetic treatment of ions and a self-consistent sodium exosphere. Ion differential energy spectra are computed for solar wind-origined protons and exopsheric sodium ions. Modeled ion and magnetic field data are discussed along the MSB6 trajectory. The results show significant variations in magnetospheric boundaries and particle populations depending on solar wind conditions. Bow shock crossings shift by up to 12 minutes across scenarios, while ion energies reach up to 10 keV for protons and 30 keV for sodium ions in the maximum solar wind case. Proton energy dispersion slopes in the plasma mantle are steeper under higher solar wind input. These findings provide critical insights into Mercury’s magnetospheric dynamics and form a foundation for interpreting BepiColombo’s upcoming observations.

The BepiColombo mission to Mercury consists of two spacecraft MPO and MIO and was launched in 2018. During the cruise phase towards the target the spacecraft performed its last close flyby near Mercury on 8 Jan 2025 (MSB6). This was the last flyby before going into orbit around the innermost planet at the end of 2026. We report on particle results from the Mass Spectrum Analyzer MSA on MIO and the Planetary Ion Camera PICAM onboard MPO together with magnetic field data MAG and hybrid simulation during this flyby. PICAM measured solar wind upstream and recorded the magnetospheric and magnetosheath plasma at various energies while MSA recorded the ion composition during the flyby including H+, He++, He+, Na+ and other heavy ions. Most of Na+ was seen near closest approach in the shadow of the planet which agrees well with AIKEF hybrid model results.

BepiColombo, the joint ESA-JAXA mission on route to the planet Mercury, was launched in 2018. After eight successful planetary flybys, the spacecraft had its final Mercury flyby on 08 Jan 2025. The PICAM (Planetary Ion Camera) instrument, part of the SERENA package, was operational from 48 hours prior to the closest encounter, until 48 hours afterwards. This ion sensor successfully monitored the upstream solar wind, as well as the magnetospheric and planetary ions at the vicinity of Mercury. Near the planet, PICAM operated in mass spectrometry mode using its Hadamard Time-of-Flight gating, which is a novel technique to improve the observations of low-density ions. We present the analysis of the ion species detected at Mercury’s environment.

Understanding Mercury's magnetosphere is a primary goal of the BepiColombo mission. In addition to spacecraft observations, numerical modeling efforts have shown to add invaluable insight to the Hermean magnetic field topology, current systems and plasma distributions. However, existing comparisons between observed and modeled data are predominantly qualitative, lacking quantitative agreement due to diverse mathematical approaches. Notably, quantitative inconsistencies of observed and modeled ion densities and energies are particularly affected. Hence, this study addresses systematic and stochastic deviations, focusing on establishing confidence intervals for "ion counting" within the hybrid AIKEF (Adaptive Ion Kinetic Electron Fluid) model. The kinetic treatment of the ions enables to directly compare model results with observations of the Planetary Ion Camera (PICAM), which is a part of the SERENA suite onboard the BepiColombo mission. Multiple ion counting methods are introduced and evaluated, including a simple sphere method, an omnidirectional method, and a field-of-view method. Our findings demonstrate that applying the field-of-view method to the modeled data, within the derived confidence interval, yields ion velocity distributions consistent with PICAM observations of Mercury’s magnetosheath. The AIKEF model and the developed analysis tools serve as a powerful and convenient method of reproducing the ion and electro-magnetic field profile around Mercury for the BepiColombo mission, both in flyby and in-orbit measurements.

Context. We use a global 3D hybrid plasma model to investigate the interaction between Mercury's magnetosphere and the solar wind for the second BepiColombo swingby, evaluate magnetospheric regions, and study the typical energy profile of protons. Aims. The objective of this study is to gain a better understanding of solar wind entry and analyze simulated plasma data along a trajectory using BepiColombo swingby 2 conditions, with the goal of enhancing our comprehension of measurement data and potentially providing forecasts for future swingbys. Methods. To model Mercury's plasma environment, we used the hybrid code AIKEF and developed a method to extract the particle (ion) data in order to compute the proton energy spectrum along the trajectory of BepiColombo during its second Mercury swingby on June 23, 2022. We evaluate magnetopause and bow shock stand-off distances under average upstream solar wind conditions with the Interplanetary Magnetic Field (IMF) condition derived from the BepiColombo magnetic field measurements during the second Mercury swingby. Results. We found that the magnetosheath on the quasi-perpendicular (dusk) side of the bow shock is thicker than that on the quasi-parallel (dawn) side, where a foreshock is formed. Multiple plasma populations can be extracted from our modeled energy spectra that assist in identifying magnetospheric regions. We observed protons of solar wind origin entering Mercury's magnetosphere. Their energies range from a few electron volts in the magnetosphere up to 10 keV in the magnetosheath.

Context. We use a global 3D hybrid plasma model to investigate the interaction between Mercury’s magnetosphere and the solar wind for the second BepiColombo swingby, evaluate magnetospheric regions, and study the typical energy profile of protons. Aims. The objective of this study is to gain a better understanding of solar wind entry and analyze simulated plasma data along a trajectory using BepiColombo swingby 2 conditions, with the goal of enhancing our comprehension of measurement data and potentially providing forecasts for future swingbys. Methods. To model Mercury’s plasma environment, we used the hybrid code AIKEF and developed a method to extract the particle (ion) data in order to compute the proton energy spectrum along the trajectory of BepiColombo during its second Mercury swingby on June 23, 2022. We evaluate magnetopause and bow shock stand-off distances under average upstream solar wind conditions with the Interplanetary Magnetic Field (IMF) condition derived from the BepiColombo magnetic field measurements during the second Mercury swingby. Results. We found that the magnetosheath on the quasi-perpendicular (dusk) side of the bow shock is thicker than that on the quasi-parallel (dawn) side, where a foreshock is formed. Multiple plasma populations can be extracted from our modeled energy spectra that assist in identifying magnetospheric regions. We observed protons of solar wind origin entering Mercury’s magnetosphere. Their energies range from a few electron volts in the magnetosphere up to 10 keV in the magnetosheath.