Transient changes in magnetospheric-ionospheric currents caused by the passage of an interplanetary shock: Northward interplanetary magnetic field case

We use results from a global MHD simulation to study the interaction of an interplanetary shock with the Earth's magnetosphere for a northward interplanetary magnetic field orientation. We connect intensifications of the transient northward Bz (NBZ) and Region 1 currents in the ionosphere with the appearance of two strong dynamo regions in the magnetosphere: the first on the high‐latitude magnetopause near and behind the cusps and the second near the equatorial plane on the flanks. The ionospheric and magnetospheric transients are well synchronized and move antisunward gradually. According to the results obtained, the source of energy for the transient NBZ current is related to shock‐intensified lobe reconnection, while the transient Region 1 current corresponds to the reflected fast shock predicted by Samsonov et al. (2007). We speculate that the electric circuits for the quasi‐stationary field‐aligned currents are similar to the transient electric circuits obtained in this paper.