A multiple‐satellite observation of the high‐latitude auroral activity on January 11, 1983

Abstract

Unusual high‐latitude auroral activity occurred on January 11, 1983, during a period of persistent interplanetary magnetic field Bz > 0, By > 0, and Bx > 0. This activity, which lasted from 0600 to 2100 UT, was characterized by numerous high‐latitude sun‐aligned arcs and a diffuse oval. Near 1500 UT a single broad (250 km) sun‐aligned arc was observed by the optical line scan system on Defense Meteorological Satellite Program (DMSP) F6. The arc was continguous with the dawn 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 allow 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 those observed by DMSP F6 but observes ion fluxes diminished by a factor of 50 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.