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.

Conjugate Observations of the Evolution of Polar Cap Arcs in Both Hemispheres

“…A few studies have shown that PCAs can coexist in both hemispheres (Carter et al, 2017;Craven et al, 1991;Cumnock et al, 2006;Gorney et al, 1986;Mizera et al, 1987;Mcewen & Zhang, 2000;Obara et al, 1988;Reidy et al, 2017). Craven et al (1991) showed that the PCAs formed symmetrically in both hemispheres, with one being the mirror image of the other.…”

Pattern of electron and ion precipitation in northern and southern polar regions for northward interplanetary magnetic field conditions

“…0148-0227 / 92/91J A-02320505.00 of an auroral oval represents the bound•ary of the polar cap' [Meng and Makita, 1986]. But this point of view is not valid when the IMF is northward, since the polar rain precipitation disappears and electrons whose energy spectrum is similar to that of precipitating particles in the poleward part of the auroral oval are seen in the polar cap [Murphree et al, 1983;Peterson and Shelley, 1984;Frank et al, 1986;Gorney et al, 1986;Rich et al, 1990].…”

Simultaneous relativistic electron and auroral particle access to the polar caps during interplanetary magnetic field Bz northward: A scenario for an open field line source of auroral particles

“…Polar cap arcs occur preferentially during prolonged periods of northward interplanetary magnetic field (IMF) and high solar wind velocity [Gussenhoven, 1982]. The main characteristics of the polar cap particle populations during the occurrence of polar cap arcs may be summarized as follows [Hardy et al, 1982;Gorney et al, 1986;Frank et al, 1986]: The arcs are created by precipitating keV electrons. The electrons neighboring the arcs can have characteristics ranging from those of weak polar rain to those of intense boundary layer electrons.…”