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Shun-ichi Akasofu's Auroral Substorm Illustrations
These are drawings made by Shun-ichi Akasofu in an article he published introducing the notion of a global aurora development, which he named substorm. In each drawing the contours of magnetic latitude are shown (60,70,80 degrees) with noon at the top of the contours, midnight at the bottom, dusk on the right, and dawn on the left. On top of the contours is a drawing of what the global aurora looks like at a particular time in the substorm evolution. At the beginning time, A. T=0, the auroral oval is quiet with a single auroral arc surrounding the magnetic pole. At time, B. T=0-5 min, another auroral arc appears around midnight and the auroral arc farthest from the pole gets brighter, as indicated by a darkening of the line representing the auroral arc. This is the growth phase. At time, C. T=5-10 min, the aurora around midnight has erupted into many arcs that move rapidly both toward the magnetic pole and away from it. This is the break-up phase and lasts through to time, D. T=10-30 min, when the recovery phase starts. In this phase, aurora is seen more and more on the dawn side of the auroral oval and the type of aurora is very different: patches of aurora that pulse on and off. This type of aurora is indicated at times, E. T=30 min-1 hr, and, F T=1-2 hour, on the right side of the magnetic latitude contours.