Kinetic effects and their role on the entry and transport of finite-size plasma jets inside the Hermean magnetosphere

Abstract

The dynamics of finite-size plasma irregularities/jets streaming across magnetic discontinuity regions, as the magnetopause, is a key process for better understanding the transport of mass, momentum and energy from the solar wind towards planetary magnetospheres. In this paper we investigate the kinetic effects and their role on the entry and transport of localized solar wind/magnetosheath plasma structures inside the Hermean magnetosphere under northward orientation of the interplanetary magnetic field. For this purpose, we use three-dimensional particle-in-cell simulations adapted to the interaction between plasma elements/irregularities/jets of finite spatial extent and the typical magnetic field of Mercury’s magnetosphere. Our simulations reveal the penetration of solar wind plasma across the Hermean magnetopause and transport inside the magnetosphere. The entry process is controlled by the magnetic field increase at the magnetopause. For reduced jumps of the magnetic field (i.e. for larger values of the interplanetary magnetic field), the magnetospheric penetration is enhanced. The equatorial dynamics of the plasma element is characterized by a dawn-to-dusk asymmetry, the braking being stronger in the dawn flank. More plasma penetrates into the dusk flank and advances deeper inside the magnetosphere than in the dawn flank. The simulation results are discussed in the context of the impulsive penetration mechanism.