Auroral currents during the magnetic storm of November 8 and 9, 1991: Observations from the Upper Atmosphere Research Satellite Particle Environment Monitor

The magnetic storm of November 8 and 9, 1991, lead to expansion of the auroral oval below 45° magnetic latitude (MLAT) and auroral phenomena were sampled by the Upper Atmosphere Research Satellite (UARS). The attitude precision and stability of UARS allow monitoring of Birkeland and ionospheric currents via magnetic field measurements from the Particle Environment Monitor (PEM) magnetometer. This paper reports the development of the intensity and location of Birkeland currents associated with this storm. Two principle results are obtained: (1) total Birkeland currents exceed 30 MA, more than 6 times nominal values, indicating Joule heating of about 3×10 12 W; (2) Birkeland currents below 50°, polar cap currents indicative of anti‐sunward convection, and cusp particle signatures of southward IMF all persist at least eight hours into recovery phase of the storm.