Effect of substorms in the Earth's nightside sector on variations in the surface atmospheric electric field at polar and equatorial latitudes

We performed an analysis of mean daily variations in the Delta Ez atmospheric electric field at the Hornsund (located near the polar cap boundary) and Kakioka (located at near-equatorial latitudes) observatories under magnetically quiet and weakly disturbed conditions. At both observatories, the mean daily variations in Delta Ez were found to be mainly controlled by the location of the observation point with respect to the focuses of the convective vortices of the DP (0) system. The substorm evolution in the nightside of the magnetosphere (a sharp burst in the AE index) was shown to lead to negative variations in Delta Ez in the dayside sector at polar latitudes (the Hornsund observatory) and positive deviations in Delta Ez at premidnight time at equatorial latitudes (the Kakioka observatory). It is concluded that variations in Delta Ez at the Kakioka observatory are largely controlled by the equatorial electrojet, which is maximal during day-time hours, and at the Hornsund observatory these variations are controlled by the auroral electrojet, which is maximal at night-time and early morning hours of local time.