Ion dynamics in the turbulent magnetotail-hidden influence of average closed field line topology

Abstract We model ion motion in the magnetotail with parabolic field lines in the presence of magnetic turbulence and cross tail constant electric field. It appeared that the average normal component and fluctuations have opposite influence on the ion dynamics. The higher is the level of magnetic fluctuations the larger is the width of the current layer and more pronounced is current splitting into double hump structure, larger is maximum temperature in the central plane and harder is the spectrum of non-Maxwellian tail of ion distribution function. At the same time average normal component causes suppression of the splitting effect and ion maximum temperature is inversely proportional to its value. Even when the amplitude of fluctuations is much higher than the average constant normal component value, ion dynamics is still controlled by the average magnetic field in the current sheet midplane.