ATMOSPHERIC ENERGY INPUT AND IONIZATION BY ENERGETIC ELECTRONS DURINGTHE GEOMAGNETIC STORM OF 8-9 NOVEMBER 1991

The Atmospheric X-ray Imaging Spectrometer (AXIS) of the Particle Envi ronment Monitor investigation aboard the Upper Atmosphere Research Sat ellite monitors energy input to the upper atmosphere due to energetic electrons. Analysis of the AXIS data from the major geomagnetic storm of 8-9 November 1991 is presented. During the November storm, electron s above a few keV flowing into a substantially expanded auroral zone p rovided the bulk of the ionizing power to the upper atmosphere. At the peak of the disturbance the total AXIS-observed power reached 40 GW. On 9 November the whole day average atmospheric ionization rate in the auroral zone at 80 lan altitude exceeded the rate due to solar UV and solar x-rays by a factor of over 10 to 100.