Polar views of the Earth's aurora with Dynamics Explorer

Preliminary examination of the first global auroral images gained with the vacuum‐ultraviolet imaging photometer on board DE 1 reveals a remarkable spatial configuration of auroral luminosities. Frequently the northern auroral oval is bifurcated by a sun‐aligned arc extending from the midday auroral zone to the nighttime sector of the oval. Simultaneous plasma measurements with the low‐altitude DE‐2 spacecraft are used to show that the character of plasmas above the polar arc is similar to those found over the poleward zones of the auroral oval. The spatial distribution of auroral luminosities is suggestive of a two‐cell structure of current systems and convection electric fields over the earth's polar cap and a similar division of the corresponding lobe in the magnetotail.