ASYMMETRIC MULTIPLE AURORAL ARCS AND INERTIAL ALFVEN WAVES

High-resolution optical observations by the University of Calgary Port able Auroral Imager show a frequent occurrence of asymmetric multiple small-scale auroral are structures during auroral substorms. Whereas t he classical multiple are array tends to exhibit a fairly symmetrical configuration, with parallel motions within individual discrete arcs b eing opposite in direction across the center of the are array, the mul tiple arcs to be discussed herein are distinguished by the presence of discrete arcs strictly equatorward of the two bright counter-streamin g arcs that would ordinarily define the center of the are array. The i ntensity of these parallel equatorward-lying arcs were in most cases f ound to decrease rapidly in the equatorward direction. By considering the topology of the structures and the spacing between arcs, observati ons are found to be consistent with recent theories suggesting inertia l Alfven waves as a possible cause of fine-scale auroral arcs.