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.
A dc electric field experiment on the Air Force satellite S3‐2 has occasionally detected intense localized electric fields near the ionosphere projection of the plasmapause. These poleward directed electric fields were observed in the pre‐midnight local time sector, seem to be related to substorm activity, and typically exceeded 100mV/m. In one case the field was 280mV/m corresponding to a drift velocity of 9.8 km/s at an altitude of 1463 km and a potential drop of 25 kilovolts. A possible source lies in the interaction between hot plasma freshly injected near magnetic midnight and the cold plasmaspheric particles. Since the potential drop is the order of the mean ring current energy, this structure may have important consequences for the understanding of magnetospheric flow patterns under disturbed conditions.
Abstract. Although it is generally accepted that extraterrestrial material is the source of metals in the upper atmosphere, the relative abundances of mesospheric metal atoms and ions present us with a conundrum. Lidar observations have consistently shown that the abundances of neutral metals in the atmosphere and the abundances of these metals in the meteoric material that falls to Earth are significantly disproportionate. The column density of neutral sodium is perhaps 2 orders of magnitude larger than that of calcium, while the abundances in meteorites are approximately equal. By contrast, ion mass spectroscopy has shown that the abundances of the meteoric ions match reasonably well those in the meteorites. We present here a model that attempts to address these discrepancies. At the heart of the model is the concept of differential ablation, which suggests that more volatile metals sublimate earlier in the descent of a cosmic dust particle than do the less volatile components. We model three different meteoric metals: sodium, magnesium, and calcium. Results suggest that sodium ablates to a greater extent than does calcium and that it ablates at a substantially higher altitude. Deposition at lower altitudes leads to more rapid conversion of the atomic calcium into complexes through three-body reactions. Thus the depletion of calcium arises from both a decrease in deposition and an increase in the rate of removal of that which is deposited. We examine the behavior of the model in several respects, comparing predicted results with measurements and finding reasonable agreement. We argue that the success of this model indicates that differential ablation is a key factor in the determination of the relative abundances of meteoric metals in the mesosphere.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.