An older video showing the progress of a typical auroral substorm. Discrete auroral arcs to the north slowly drift south until an instability triggers a substorm, in this case somewhere to the west of the observer so the bright and very dynamic aurora sweeps across the sky from the west. After the substorm discrete arcs are pushed back north while diffuse and pulsating aurora fill the sky overhead and to the south. The video illustrates the need for fast glass and high ISO to be able to reproduce any detail in substorm aurora when shooting timelapse. Canon 350D with Peleng f/3.5 circular fisheye, 10 sec exposures @ ISO1600. Actual time between shots is ~14 seconds, compiled at 24fps. Captured near Fairbanks, Alaska.