Evidence for current sheet acceleration in the geomagnetic tail

The existence of the current sheet and the dawn to dusk electric field in the geomagnetic tail implies there is particle energization in the tail current sheet of the order 2–10% of the total solar wind energy incident upon the dayside magnetopause. In this paper we determine that ion acceleration in a current sheet with a small magnetic field across the sheet, via single‐particle motion which violates the guiding center approximation, can account for this large energization in the tail. We calculate the distribution of accelerated ions which result from the current sheet acceleration and compare the results with distributions of accelerated ions frequently observed flowing earthwards along the outer boundary of the plasma sheet. The comparison indicates that the observed earthward‐flowing ions result from current sheet acceleration. Comparison with measurements of auroral ion precipitation at low altitudes implies that the accelerated ions ejected from the current sheet are also an important source of auroral ion precipitation. In addition, these accelerated ions may be an important source of plasma sheet ions.