Polar cap electric field structures with a northward interplanetary magnetic field

Abstract

Polar cap electric fields patterns are presented from times when the S3‐2 Satellite was near the dawn‐dusk meridian and IMF data were available. With Bz ≥ 0.7 γ, two characteristic types of electric field patterns were measured in the polar cap. In the sunlit polar cap the convection pattern usually consisted of four cells. Two of the cells were confined to the polar cap with sunward convection in the central portion of the cap. The other pair of cells were marked by anti‐sunward flow along the flanks of the polar cap and by sunward flow in the auroral oval. These observations are interpreted in terms of a model for magnetic merging at the poleward wall of the dayside polar cusp. The sunward flow in the auroral zone is not predicted by the magnetic model and may be due to a viscous interaction between the solar wind and magnetosphere. The second type, which was observed in some of the summer hemisphere passes and all of the winter ones, was characterized by an electric field pattern which was very turbulent, and may be related to inhomogeneous merging.

Measuring the dayside reconnection rate during an interval of due northward interplanetary magnetic field

“…In this picture, plasma at the footprint of the reconnection X-line convects sunward, due to the magnetic tension of the newly-reconnected field lines, before being swept antisunward towards dawn and dusk with the magnetosheath flow. Early observations of ionospheric flow during northward IMF conditions showed the existence of sunward convection within the polar cap ionosphere (Maezawa, 1976;Burke et al, 1979). Further observations illustrated that "four-cell" convection was typical during these conditionstwo reverse convection cells within the polar cap, with two "normal" convection cells, thought to be driven by viscous processes at the magnetopause, at lower latitudes (Heelis et al, 1986;Knipp et al, 1991;Freeman et al, 1993;Reiff and Heelis, 1994;Cumnock et al, 1995).…”

A decade of the Super Dual Auroral Radar Network (SuperDARN): scientific achievements, new techniques and future directions

“…Whereas the morphology of ionospheric convection during intervals dominated by southward IMF was well established before the SuperDARN era, there was disagreement over the form of ionospheric convection during intervals of strongly northward IMF. Early studies (Burke et al 1979;Reiff and Burch 1985) suggested the existence of four convection cells during northward IMF conditions-two ''reverse'' cells at high-latitudes driven by lobe reconnection antisunward of the cusp regions, and two ''normal'' cells at lower latitudes driven by viscous processes at the magnetopause. However, Heppner and Maynard (1987) argued that there might not be four convection cells but only two, highly distorted cells.…”

Driving dayside convection with northward IMF: Observations by a sounding rocket launched from Svalbard

“…The two merged ends with both feet in the solar wind simply blow away through the magnetosheath [Maezawa, 1976]. For the described interplanetary conditions a lobe cell is embedded within the convection cell [Burke et al, 1994]. Crooker and Rich [1993] showed that the ionosphere with the embedded lobe cell is favored to be in the summer hemisphere and has larger potential drops than the corresponding winter hemisphere convection cell.…”