Magnetic Turbulence and Ion Dynamics in the Magnetotail

The ion dynamics in the Earth's magnetotail is studied in the case when a cross tail electric field E0 and reconnection-driven magnetic turbulence are present in the current sheet. The magnetic turbulence observed by the Interball spacecraft is modeled numerically by a power law magnetic fluctuation spectrum. A test particle simulation is performed for the ions, and the distribution function moments are obtained as a function of the magnetic fluctuation level, δB/B0, and of the value of the normal component Bn. It appears that even in the presence of magnetic turbulence, the normal component has a marked influence on particle dynamics: the ion bulk velocity along Ey and ion temperature are almost inversely proportional to Bn. The magnetic turbulence causes the current to split in two layers, and the level of magnetic fluctuations needed to have splitting is roughly proportional to Bn. It appears that in the relevant range of parameters, Bn and δB/B0 have opposite effects on the current structure and on ion heating.