A Great Auroral Substorm. The great auroral substorm over the Southern Hemisphere as observed with Dynamics Explorer 1 from 0202 to 0517 UT on 13 June 1983 is shown here in a 16-image sequence. Substorm onset is observed with the first image of the sequence, at upper left. The aurora advances poleward in the midnight sector for ~ 2 ½ hours (the first 12 images) as the spacecraft approaches auroral latitudes and lower altitudes. With the last four images the aurora is observed to decline in luminosity and the area of the dark polar cap increases as the aurora retreats to lower latitudes in the midnight sector. The passband of the optical filter is 136-165 nm, for which the dominant responses are from emissions in the LBH bands of molecular nitrogen. The terrestrial ring current, as measured with the Dst index, is observed to grow rapidly during the expansive phase of this substorm. Hourly averages of the Dst index decrease by 150 nT (nanoteslas) in the four-hour period beginning with substorm onset.