Interplanetary magnetic field control of high‐latitude electric fields and currents determined from Greenland Magnetometer Data

To determine the effects of the interplanetary magnetic field (IMF) on the electric potential as well as on ionospheric and field‐aligned currents, a recently available numerical algorithm is applied to an empirical model of high‐latitude magnetic perturbations, parameterized in terms of the B y and B z components of the IMF. The empirical model is derived from 20‐min average magnetometer data observed during summer at the chain on the west coast of Greenland and the corresponding IMF information from the HEOS 2 satellite. The calculated results reproduce fairly well overall features of the influence of the IMF on high‐latitude electric fields which have been reported on the basis of more direct measurements. This confirms the validity of the numerical method and the conductivity distribution models. In addition, our results indicate that the system of ionospheric and Birkeland currents near the polar cusp, which has been shown to depend strongly on B y , exists independently of the system of region 1 and region 2 field‐aligned currents, which, on the other hand, depends strongly on B z . The direction of the field‐aligned currents in the dayside polar cap is uniquely controlled by the sign of the B y component of the IMF, namely upward currents for B y > 0 in the northern polar cap and oppositely directed for B y < 0. At the dayside boundary of the polar cap the DPY ionospheric Hall current is sandwiched between the polar cap field‐aligned currents and an oppositely directed field‐aligned current sheet on the equatorward side. For B z >0 and B y small the ionospheric and field‐aligned currents are localized near the dayside polar cusp, and the electric field has a dusk‐dawn component in a narrow region near magnetic local noon in agreement with reported satellite measurements. The associated distribution of field‐aligned currents consists of the region 1 current system and an additional pair of oppositely directed currents located poleward of the region 1 currents.