Events of August 2, 2002: Features of Substorm Field-Aligned Currents

A model of alignment of the field-aligned current generator system in the disturbed magnetosphere is proposed. It has been found that Pedersen currents in the disturbed ionosphere of the auroral oval are meridional. They connect oppositely directed field-aligned currents (FACs) of two adjacent Iijima and Potemra (IP) regions. This supplements the dominant concept of currents in the literature, in which a substorm current wedge plays a major role. During the considered substorm, graphs have been obtained of changes in FAC intensities in each of the three Iijima and Potemra regions of the Northern Hemisphere. These new data suggest that during a disturbance, the Region 1 FAC and the sum of regions 2 and 0 FACs remain equal. The equality means that these three generators form a unified system. Inequalities of intensities between two FACs of different sign simultaneously observed in the dawn and dusk sectors have also been detected in each IP region. A conceptual model is proposed for the formation of this dawn-dusk asymmetry. In the model, in addition to FACs that close up in the ionosphere of the Northern Hemisphere, FACs connecting the two hemispheres are also presented. The conclusion is justified that the global magnetospheric dynamo operates as a voltage generator under relatively quiet (average) conditions, as during storms.