Auroral boundary correlations between UVI and DMSP

[1] Equatorward and poleward auroral boundaries from latitude profiles of Polar Ultraviolet Imager (UVI) auroral images were correlated with over 23,000 boundaries derived from 2 years of Defense Meteorological Satellite Program (DMSP) electron precipitation data. Latitude differences between DMSP and UVI boundaries were averaged into 1-hour and 3-hour sectors of magnetic local time (MLT). The statistical distributions of these differences generally peak near zero but have Gaussian-like shapes with widths of about 3°–4° in magnetic latitude. The mean values of these offsets exhibit systematic trends in MLT, with the largest disagreement near 05 MLT for the poleward boundaries and near noon for the equatorward boundaries. The mean offsets were fit to second-order harmonic expansions, which approximately “calibrate” image boundaries with respect to the precipitating electron boundaries. The harmonic fits suggest that the images can yield approximate precipitation boundaries for such purposes as estimating the area of the polar cap.