Auroral current system as estimated by a magnetic inversion method

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The spatial distribution of field-aligned currents(FACs) is studied for an intense substorm. We first estimated the height-integrated ionospheric Hall and Pedersen conductances from ultraviolet images taken by the Polar satellite. To derive FACs, we then employed Ohm's law for the ionosphere, applying a magnetic inversion method to the input conductances and ground magnetic field data. As a result, the Hall FACs that are connected to the ionospheric Hall currents were aniti-correlated with the Pedersen FACs that are connected to the ionospheric Pedersen currents. Such anti-correlations were observed near the poleward and the equatorward edges of the auroral westward currents. This result indicates that the auroral current system included the Cowling channel that is the auroral westward currents enhanced by the polarization electric field in this particular event.