Solar wind entry into Mercury's magnetosphere: Simulation results for the second swingby of BepiColombo

TL;DR

This study uses a 3D hybrid plasma model to simulate solar wind entry into Mercury's magnetosphere during BepiColombo's second swingby, revealing plasma entry regions and proton energy profiles.

Contribution

It introduces a novel simulation approach to analyze Mercury's magnetospheric response during BepiColombo's second swingby, enhancing understanding of solar wind entry mechanisms.

Findings

Magnetosheath is thicker on the quasi-perpendicular side.

Multiple plasma populations help identify magnetospheric regions.

Solar wind protons enter the magnetosphere with energies up to 10 keV.

Abstract

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.