HIGH TIME RESOLUTION STUDY OF THE HEMISPHERIC POWER CARRIED BY ENERGETIC ELECTRONS INTO THE IONOSPHERE DURING THE MAY 19 20, 1996 AURORAL ACTIVITY/

The ultraviolet imager (UVI) on board the POLAR satellite offers the o pportunity to obtain high time resolution global auroral images. The s pectral discrimination of the imager is sufficient to separate the aur oral far ultraviolet emissions from the scattered sunlight, even when the entire auroral Bone is sunlit. The energy flux of the precipitatin g electrons is derived from the surface brightness through the LBH-lon g filter. Global images which have the dayglow removed are spatially i ntegrated to yield the total rate of energy input into the northern he misphere. This parameter, the hemispheric power, has found much applic ation in ionospheric modeling. It can also be derived from electron sp ectra measured along the track of the NOAA/TIROS satellites that are c ombined with average empirical auroral precipitation patterns. We show that the hemispheric power derived from the two-dimensional images re presents a substantial improvement in the temporal variability of this parameter. We present an example for the period of 19/20 May 1996 by comparing the hemispheric power derived from NOAA/TIROS measurements w ith those derived from the UVI images.