Work

Effects of interior conductivity on solar wind proton precipitation on Mercury

Year: 2026

Type: article

Abstract: Context. Mercury is an airless body where space weathering processes play a key role in modifying the surface and sustaining the exosphere. Some of these processes are thought to be linked to ion precipitation driven by solar wind–magnetosphere interactions, although the detailed mechanisms remain to be fully understood. Previous studies of solar wind proton precipitation have mainly focused on external factors, such as solar wind and interplanetary magnetic-field conditions, while the role of internal factors has received comparatively little attention. Aims. We aim to investigate how Mercury’s interior conductivity profile, an internal factor, affects solar wind proton precipitation onto the planet’s surface. Methods. We employed Amitis, a hybrid simulation model, to conduct a series of simulations with different interior conductivity profiles and examine their precipitation patterns. We then separated the magnetic fields generated by interior currents from those of other sources to isolate their respective contributions to precipitation. Results. We find that core induction currents shield the equatorial region from precipitation, while interior conduction currents linked to Region-1 field-aligned currents (R1 FACs) reduce dayside shielding and enhance nightside shielding, thereby modulating the day–night asymmetry of the precipitation pattern. In addition, the R1 FAC-related electric field enhances the dawn–dusk asymmetry of precipitation. Conclusions. These findings indicate that the interior conductivity profile substantially influences the solar wind proton precipitation pattern through its associated magnetic and electric fields, with effects that extend beyond the surface into Mercury’s broader coupled environment. The planetary interior should be recognized as an integral component of Mercury’s coupled space environment – alongside the solar wind, magnetosphere, surface, and exosphere – and should not be neglected in future modeling and observational studies.

Source: Astronomy and Astrophysics

DOI: 10.1051/0004-6361/202662560