Influence of the east-west component of the interplanetary magnetic field on the intensity of the auroral electrojet

Abstract Analysis of interplanetary data has been made to evaluate the influence of the Bin y component of the IMF on the magnitude of the AL index, especially with reference to the contribution of B y in the reconnection process between the IMF and geomagnetic fields in the dayside part of the magnetosphere. The results of the analysis showed that the effect of Bin y on AL is predominantly of a different type from that expected by the current theory of reconnection, and the B y effect of the latter type was found to be much less significant in magnitude than the theory predicts. The discrepancy may be resolved if the region where the reconnection takes place has an elongated shape.