Snapshots of High-Latitude Electrodynamics Using Viking and DMSP F7 Observations

Simultaneous observations by the Viking and the DMSP F7 satellites have been used as input to a new method to obtain snapshot pictures of the auroral electrodynamics. In particular, an instantaneous global equipotential (or convection) pattern is calculated from distributions of field-aligned current and conductivity which are qualitatively consistent with the Viking auroral imager data and quantitatively consistent with magnetic field and particle data from the two satellites. This convection pattern, which is of the normal two-cell type, with a weak dusk cell and a strong, elongated crescent- shaped dawn cell (consistent with positive interplanetary magnetic field By), agrees well with the Viking electric field data. The model and the observed potential profiles agree nicely along the entire Viking orbit except for two intervals above acceleration regions where deviations are to be expected (due to parallel electric fields). These regions are characterized by U-shaped potential minima, upward field-aligned currents, upgoing ion beams, and relatively intense auroral kilometric radiation. Thus, the model results are consistent with the Viking observations not only on a global scale but also on the scale of the auroral acceleration regions. The corresponding convection in the magnetosphere is obtained from a simple projection to the equatorial plane of the deduced two-cell convection pattern. From this the location of the plasmapause is inferred. Aurora, Ionosphere, Reprints. Pub. in Jnl. of Geophysical Research, v93 nA12 p14,479-14, 492, 1 Dec 1988.