Influence of the Dipole Tilt Angle on the Development of Auroral Electrojets

Abstract

Influence of the tilt angle of the geomagnetic dipole, χ, on the development of auroral electrojets was investigated paying attention to the relation with solar wind parameters. Indices AU and AL were used as the measures of the intensities of the eastward and the westward electrojets, and were found to have evident χ dependences under the normalized condition of the solar wind velocity, V, and of the GSM southward component, B_s, of the interplanetary magnetic field (IMF). The main characteristics of the influence of χ are as follows. (1) AL shows very different χ dependences for different signs of the B_y component of the IMF. The χ dependences of AL are not independent of its dependence on B_s and V, and hence they have a close relationship with the substorm process initiated from the reconnection of the IMF and geomagnetic field lines at the dayside magnetopause. (2) AU shows very similar χ dependences regardless of the sign of B_y. The enhancement of AU in the positive range of χ can be interpreted as indicating the important role of solar radiation in determining the magnitude of eastward electrojets.