IMAGING OF ARTIFICIAL AURORA IN THE UPPER-ATMOSPHERE

We use continuum (white light) and filtered (427.8 nm) images from the Atmospheric Emissions Photometric Imaging (AEPI) experiment on the At mospheric Laboratory for Applications and Science (ATLAS) 1 shuttle mi ssion to investigate the shape and evolution of artificial amoral patc hes generated by the Space Experiments with Particle Accelerators (SEP AC) electron beam experiment, Auroral patches generated by this beam e xperiment are complex and differ in the white light and filtered image s. In the white light images, the amoral patch consists of a relativel y large, diffuse, and somewhat symmetric head and a tail that is direc ted approximately opposite the spacecraft velocity vector. From the gr owth df the tail during a beam pulse, the distance from the imager to the emissions is estimated to be about 200 km, consistent with expecta tions from a simple model of amoral emissions in the atmosphere. In ad dition to the amoral patch, an intense, diffuse, and variable backgrou nd glow filling essentially the entire field of view of the white ligh t imager is seen during the beam pulses, This background glow may be c aused by low-energy electrons very near the shuttle. This glow is abse nt in the filtered images, in which the shape of the amoral patch diff ered, consisting of a relatively large, diffuse, but more asymmetric h ead, a tail, and a smaller and less intense spot below the head. Curva ture of the magnetic field and spacecraft motion during the 1-s filter ed images allows an estimate of the relative distance from the shuttle to the head, tail, and small spot, This shape is consistent with head emissions generated relatively near the spacecraft (nearest few kilom eters), tail emissions somewhat farther away, and finally the small sp ot emissions generated the farthest away in the lower atmosphere where the natural auroras would be created. In addition, the shape of these patches in the filtered images suggests that the risetime for the hea d and tail emissions in the filtered images appears to be longer than that for the-small spot emission. The differences between the white li ght images and the filtered images are consistent with the difference between the emission parent state lifetimes and the energy requirement for the emission production. The white light images contain emissions with long lifetimes, and these emissions which are produced near the observer are swept out of the field of view because they are left behi nd by the shuttle. This gives a bias toward emissions generated farthe r from the orbiter. The filtered images contain only the very fast pro duced N-2(+) emission with a substantial component generated near the orbiter and with an inverse square law attenuated auroral spot in the lower atmosphere. The presence of the tail and the apparent risetime i n the near-field emission suggest that there is a buildup and decay ti me associated with the hot plasma created by the electron beam.