Transmission of polar electric fields to the Equator

Abstract

SEVERAL kinds of geomagnetic variations are observed simultaneously at high latitudes and in the equatorial region. These are substorms or DP-1 variations, S^p_q or DP-2 variations, some kinds of pulsations, and the DS-part of SSC and SI. Araki¹ analysed the relationship of the preliminary reverse impulse of SC^* occurring in the high-latitude and the equatorial regions and found that their occurrence in both regions is well correlated, almost simultaneous, and that the waveforms are very similar. From the characteristics of these geomagnetic variations, it seems that a horizontal electric field impressed in the polar ionosphere from the magnetosphere greatly contributes to the equatorial part of these geomagnetic variations. This electric field is generated by large scale dynamic processes in the magnetosphere such as a sudden compression by an interplanetary shock wave or a change of the magnetospheric convection, and its direction will be approximately east–west (dawn–dusk)². To clarify the mechanism of the instantaneous horizontal transmission of the polar electric field, we have analysed the response of the ionosphere to a suddenly impressed electric field.