The current sheet flapping motions induced by non-adiabatic ions: case study

Abstract. In this paper, we analyzed the y-component of magnetic field line curvature in the plasma sheet and found that there are two kinds of shear structures of the flapping current sheet, i.e. symmetric and antisymmetric. The alternating bending orientations of guiding field are exactly corresponding to alternating north-south asymmetries of the bouncing ion population in the sheet center. Those alternating asymmetric plasma sources consequently induce the current sheet flapping motion as a driver. In addition, a substantial particle population with dawnward motion was observed in the center of a bifurcated current sheet. This population is identified as the quasi-adiabatic particles, and provides a net current opposite to the conventional cross-tail current.