Electric and magnetic drift of non-adiabatic ions in the Earth's geomagnetic tail current sheet

It has been shown recently that non-adiabatic particles in the Earth's magnetotail drift across the tail roughly as predicted for adiabatic particles with 90° pitch angles. In this paper we show that this result implies the existence of an approximate invariant of the motion. Adding the effect of convection associated electric fields, we can then obtain the approximate bounce averaged motion of non-adiabatic particles in the magnetotail. Thus the particle motion and energization due to combined magnetic and electric drifts in the magnetotail are easily predicted.