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 opportunity to obtain high time resolution global auroral images. The spectral discrimination of the imager is sufficient to separate the auroral far ultraviolet emissions from the scattered sunlight, even when the entire auroral zone is sunlit. The energy flux of the precipitating electrons is derived from the surface brightness through the LBH‐long filter. Global images which have the dayglow removed are spatially integrated to yield the total rate of energy input into the northern hemisphere. This parameter, the hemispheric power, has found much application in ionospheric modeling. It can also be derived from electron spectra measured along the track of the NOAA/TIROS satellites that are combined with average empirical auroral precipitation patterns. We show that the hemispheric power derived from the two‐dimensional images represents 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 with those derived from the UVI images.