The Diffuse Auroral Eraser

The source of diffuse aurora has been widely studied and linked to electron cyclotron harmonic and upper-band chorus waves. It is known that these waves scatter 100s of eV to 10s of keV electrons from the plasma sheet, but the relative contribution of each wave type is still an open question. In this study, we report an interesting and unusual auroral feature observed on March 15, 2002. We believe that these observations could help further our understanding of waves associated with diffuse aurora. This diffuse auroral feature is characterized by four phases: (1) the initial phase exhibiting regular diffuse aurora; (2) the brightening phase, where an east-west auroral stripe rapidly brightens; (3) the eraser phase, where the stripe dims to below its initial state; and (4) the recovery phase, where the diffuse aurora returns to its original brightness. Using a superposed epoch analysis of 22 events, we calculate the average recovery phase time to be 20 s, although this varies widely between events. We hypothesize that the process responsible for these auroral eraser events could be the result of chorus waves modulating diffuse aurora.