Ion transport through the turbulent magnetopause: Calculations of the distribution function moments

A numerical study of magnetosheath (MSH) ion motion in the magnetopause current sheet (MCS) in the presence of magnetic fluctuations is reported. Test particles are injected at the MSH side only. The magnetic field turbulence is modeled as a power law spectrum in phase space, which reaches maximum intensity in the center of the MCS, and decreases towards the MSH and magnetosphere (MSP) boundaries, creating magnetic islands. The number of particles entering the MSP, reflected from the magnetopause and flowing away from the flanks is computed, as a function of the fluctuation level of the turbulence and of the sheared magnetic field. All those quantities appear to be strongly dependent on the fluctuation level, with the number of particles entering the magnetopause increasing with the fluctuation level. We calculate particle density, bulk velocity and temperature. It appears that temperature and bulk velocity are increasing in the direction normal to the magnetopause, while density is decreasing, in a qualitative accordance with the observations. We also study the influence of velocity of injected ions on the moments of particle distribution function.