ANALYSIS OF A POLAR AURORAL ARE OBSERVED FROM EUREKA (89-DEGREES-N) AND BY DMSP SATELLITES ON DECEMBER 14, 1990

A bright and long-lived Sun-aligned auroral are was observed over the north magnetic pole from 1120 to 1220 UT, December 14, 1990 at Eureka, Canada. It was monitored through its full lifetime with high resoluti on with an all-sky imager and a meridian scanning spectrometer. Its me asured off-zenith 5577-Angstrom intensity reached 12 kR. The recorded electron flux obtained by a DMSP F9 overpass at 1124:15 UT was 56 ergs /(cm(2) s sr), yielding an inferred 5577-Angstrom intensity in that re gion of the are of at least 80 kR. The are drifted slowly in the dusk to dawn. direction during its early stages, then reversed its drift di rection during later stages. The characteristics of the polar are (its intensity, duration, and small-scale dynamics) were very similar to t hose of auroral oval arcs and strongly suggest that the polar are occu rred on closed magnetic field lines. Emissions on the duskside of the are further suggest that the region of closed magnetic field lines ext ended from the evening sector to the magnetic pole. The inference is t hat the interplanetary magnetic field was most likely B-z northward an d B-y positive during the period of appearance of the are.