The possible influence of MHD turbulence on the energy distributions of ions in the Earth's plasma sheet was studied using data taken by the THEMIS satellites. Turbulence levels were traced using eddy diffusion coefficients (D), of which we measured one for each Geocentric Solar Magnetospheric (GSM) coordinates every 12 min. Ion fluxes between 1.75 and 210.5 keV during the same time windows that correspond to mainly suprathermal populations were fitted to Kappa distribution functions, which approximate a Maxwellian distribution when theκ-index (κ) is large. We found that the distribution of the eddy diffusion coefficients is bimodal, independently of both the eddy diffusion component and the plasma beta (β) parameter, which is defined as the ratio between plasma and magnetic pressures. The main peak corresponds to turbulent plasma flows withD> 103km2s−1. In such cases, the impact of turbulence on theκindex depends on the value ofβand also on the direction of the turbulent transport. For eddy diffusion perpendicular to the neutral sheet, the values ofκdecrease asDzzincreases forβ< 2; while for higher values ofβ,κincreases withDzz. For the other two directions, the values ofκdecrease asDincreases. This last tendency is stronger forβ~ 1 but almost null forβ~ 10. The secondary peak in the distribution ofDvalues might represent quasi-laminar flows forming part of very large vortices, correct detection and description of which is beyond the scope of this study.
