PHOTO RELEASE: 96-38

COMPLETE NORTHERN AURORAL OVAL OBSERVED -- This photo shows a spectacular view of the full northern auroral oval in ultraviolet light, seen as a "crown" in the top portion of the image. The Earth is imaged from the Polar spacecraft from an altitude of 16,160 miles (25,740 kilometers) over the southern border of Alaska near local noon on March 25, 1996. The picture was taken by the Earth Camera, one of three cameras in the Visible Imaging System on the Polar satellite. Advances in technology for the construction of these cameras allow the auroral light to be extracted from the sunlit atmosphere with unprecedented clarity, as amply demonstrated by this picture of a complete auroral oval that extends well into the sunlit atmosphere. The extended region of light in the center and bottom of the image is the glow from the Sun's illumination of Earth's upper atmosphere. The filter for this image passes ultraviolet emissions that are not directly visible to the human eye. The intensities of this light from atomic oxygen in Earth's atmosphere at altitudes in the range of about 60 to 300 miles (100 to 500 kilometers) are color coded in the image with dark red as lowest intensities and whitish yellow as the brightest intensities. A coastline has been superposed on the image. Note that the aurora is positioned just north of the Great Lakes on the dayside of the Earth and over the Scandinavian peninsula on the far nightside of the Earth. The Visible Imaging System was designed and constructed at The University of Iowa. The principal investigator for the instrument is Dr. Louis A. Frank and the instrument scientist and manager is Dr. John B. Sigwarth, both from The University of Iowa.