Self-consistent stabilization of large-scale linear magnetic holes via ion trapping

Magnetic holes (MHs) are localized depressions in the magnetic field commonly observed in space plasmas such as the solar wind, planetary magnetosheaths, and cometary environments. Despite the abundance of spacecraft observations, the mechanisms governing the generation of these structures are not fully understood. In this study, we investigate the stability of magnetic depressions in a controlled plasma environment via two-dimensional hybrid particle-in-cell simulations using the Menura code. Initializing the system with preexisting magnetic field depressions embedded in a mirror-stable plasma allows us to isolate the fundamental physical mechanisms responsible for stabilization and equilibrium. We analyze the roles of the initial depth, characteristic width, and magnetic field geometry of the depression. Our results demonstrate that narrow depressions (of the order of ion kinetic scales) are unstable, whereas broader structures can reach stable equilibria through ion trapping, resulting in localized density enhancements and temperature anisotropy consistent with in situ observations of large-scale MHs. The findings highlight the importance of ion trapping for stabilization and provide a controlled framework to investigate MH dynamics.