Hybrid Simulations of the Intrinsic Magnetic Fields Effect on Planetary Oxygen and Hydrogen Ion Escape at Mars: Ancient-to-Present Evolution

The present study employs self-consistent three-dimensional global hybrid simulations of Mars–solar wind interactions to investigate how intrinsic magnetic fields regulate the escape of planetary ions with different masses, with escaping ion trajectories traced. Present-day Martian crustal magnetic fields modify ionospheric ion escape primarily by restructuring local electric and magnetic field configurations. First, they alter the magnetic topology (closed, open, or draped), inclination and intensity of magnetic field lines, thereby increasing local ion density and facilitating outward transport along open field channels. Second, they reduce the radial component of the local electric field, which directly influences ion acceleration.

The combined effects preferentially enhance the escape of heavy oxygen ions while suppressing the escape of light hydrogen ions, mainly because light ions are more effectively trapped within strong closed crustal magnetic loops. Finally, we extend our investigation to ancient Mars conditions and compare how intrinsic magnetic fields in early and present epochs differently regulate planetary ion escape, providing insight into the long-term evolution of the Martian atmosphere.