The effect of interplanetary magnetic field orientation on the solar wind flux impacting Mercury's surface

TL;DR

This study uses MHD simulations to analyze how different orientations of the interplanetary magnetic field affect solar wind flux and plasma flows on Mercury's surface, revealing orientation-dependent variations in magnetospheric behavior.

Contribution

It provides a detailed simulation-based analysis of Mercury's magnetospheric response to six realistic interplanetary magnetic field configurations, highlighting orientation-specific effects.

Findings

Magnetic field weakening in certain orientations enhances surface flows.

Fluxes are reduced and drifted to poles or equator depending on orientation.

Magnetosphere tilt and weakening depend on magnetic field alignment.

Abstract

The aim of this paper is to study the plasma flows on the Mercury surface for different interplanetary magnetic field orientations on the day side of the planet. We use a single fluid MHD model in spherical coordinates to simulate the interaction of the solar wind with the Hermean magnetosphere for six solar wind realistic configurations with different magnetic field orientations: Mercury-Sun, Sun-Mercury, aligned with the magnetic axis of Mercury (Northward and Southward) and with the orbital plane perpendicular to the previous cases. In the Mercury-Sun (Sun-Mercury) simulation the Hermean magnetic field is weakened in the South-East (North-East) of the magnetosphere leading to an enhancement of the flows on the South (North) hemisphere. For a Northward (Southward) orientation there is an enhancement (weakening) of the Hermean magnetic field in the nose of the bow shock so the fluxes are reduced and drifted to the poles (enhanced and drifted to the equator). If the solar wind magnetic field is in the orbital plane the magnetosphere is tilted to the West (East) and weakened at the nose of the shock, so the flows are enhanced and drifted to the East (West) in the Northern hemisphere and to the West (East) in the Southern hemisphere.