The latitudinal distributions of auroral zone electric fields and ground magnetic perturbations and their response to variations in the interplanetary magnetic field

Chatanika observations of latitudinal distributions of convection electric fields (E ⊥ ) are compared with isointensity Δ H contours in latitude and time from the Alaskan magnetometer chain and with the north‐south component of the interplanetary magnetic field (IMF B zm ) from Imp‐J. As expected, northward electric fields were generally observed within latitude and time regions where Δ H was positive, while southward electric fields were observed within negative Δ H regions. However, correlation between the magnitudes of the electric fields and of the Δ H perturbations was not strong, owing to variability in ionospheric conductivities produced by precipitation and solar illumination. In the midnight sector the northward‐to‐southward transition in the electric field and positive‐to‐negative Δ H transition were roughly collocated (to within 1 hour in local time) as signatures of the Harang discontinuity. The most important findings are that (1) southward (northward) IMF B zm transitions caused rapid equatorward (poleward) shifts of the electric field and Δ H patterns and (2) southward IMF B z transitions, magnetospheric substorms, and local time transitions of the Harang discontinuity can all lead to northward‐to‐southward transitions of the electric field in the midnight sector. Due to the interlaced phasing of each of these three causal mechanisms a highly complex temporal pattern of electric fields results.