Hall current as a source of the cross-tail current interruption,the asymmetric main phase field and the poleward expanding auroral bulge

It is suggested that the ionosphere plays an active role in many substorm processes by generating field-aligned currents associated with the Hall current. Various substorm phenomena, such as the cross-tail current interruption, the asymmetric main phase field and the poleward expanding auroral bulge, may be closely related to the closure of the Hall current circuits in the magnetosphere.