Current carriers in the near‐Earth cross‐tail current sheet during substorm growth phase

Abstract

Throughout most of the growth phase of a substorm, the cross‐tail current at x ∼ −10 R e can be supplied by the curvature drift of a bi‐directional field aligned distribution of ∼1 keV electrons. Just prior to its local disruption after substorm onset, the cross‐tail current in the now thin (∼400 km) current sheet is carried by the cross‐tail serpentine motion of non‐adiabatic ions (Speiser, 1965). The instability of this latter current leads to the local disruption of the near‐earth current sheet.