Contribution of nonadiabatic ions to the cross-tail current in an O+ dominated thin current sheet -: art. no. A06213

[ 1] During storm times, O+ can dominate both the pressure and the density in the plasma sheet. Because of the contribution from ion outflow, the plasma sheet is already oxygen-rich prior to substorm onset. At substorm onset the fraction of O+ contributing to the pressure and density increases. In the O+ dominated thin current sheet the O+ ions are observed to stream from dawn to dusk across the tail, as predicted for nonadiabatic ions by Speiser ( 1965). We calculate the current contribution from these ions and find that they carry about 5-10% of the cross-tail current. During a nonstormtime substorm the general behavior of the O+ is the same. However, because there is less O+ present, the O+ never dominates over H+, and the contribution to the cross-tail current is even less.