A Multiple-Satellite Observation of the High-Latitude Auroral Activity on 11 January 1983

Unusual high latitude auroral activity occurred during a period of persistent IMF Bz 0, and Bx . 0. This activity was characterized by numerous high latitude sun aligned arcs and a diffuse oval. A single broad (250 km) sun aligned arc was observed by the optical linescan system on DMSP-F6. The arc was contiguous with the drawn auroral oval and extended across the northern polar cap, similar to previously reported 'theta aurora' configurations. The fortunate orbital locations of the DMSP-F6, NOAA-7 and NOAA-6 satellites allows a detailed analysis of the precipitating particle populations responsible for both the sun aligned arc and oval auroras. Specifically, NOAA-7 and DMSP-F6 cross the broad sun aligned arc almost simultaneously in the northern hemisphere, with NOAA-7 crossing the arc 1500 km farther toward the dayside. During the arc crossing, NOAA-7 observes electron fluxes, temperatures and accelerations similar to DMSP-F6, but observes ion fluxes diminished by a factor of fifty in comparison with DMSP. Almost simultaneously NOAA-6 crosses the southern polar cap and observes flux levels in an apparent high latitude arc comparable to those observed by DMSP. The results are consistent with, but supplementary to, previous observations of high latitude auroral observations and thus place meaningful constraints on emerging theoretical concepts of this phenomenon. Prepared in cooperation with Lockheed Palo Alto Research Lab., CA.