The Dynamic Aurora. Twelve consecutive false-color images of the northern auroral oval record the onset and evolution of a substorm as the spacecraft Dynamics Explorer 1 descends from apogee position during the period 0529 through 0755 UT on 2 April 1982. Each image is telemetered in a twelve minute interval. The poleward bulge of the surge is first seen in the fourth image, which begins at 0605 UT. A westward traveling surge then propagates along the poleward edge of the oval as highly structured, eastward-moving auroral forms develop in the post-midnight sector. The sunlit atmosphere is visible at the upper left in each image. The passband of the optical filter is 123-155 nm, for which the dominant responses are from emissions of atomic oxygen at about 130.4 and 135.6 nm and the LBH bands of molecular nitrogen. The spacecraft location for the first image at the upper left-hand corner of the image sequence is 23° N geographic latitude and 22 hours local time, and the altitude is 3.67 earth radii. The spacecraft is directly over the auroral oval as the last image frame is telemetered, at an altitude of 2.17 earth radii.