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 E-o 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, deltaB/B-o, and of the value of the normal component B-n. 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 E-y and ion temperature are almost inversely proportional to B-n. 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 B-n. It appears that in the relevant range of parameters, B-n and deltaB/B-o have opposite effects on the current structure and on ion heating.