Measuring the Thickness of Auroral Curtains

Abstract

Auroral arcs (curtains) are extremely thin. A calculation of the minimum-possible are thickness is presented; this minimum thickness is found to be about 9.5 m. Four requirements for designing an optical system that can image the thinnest curtains are discussed: 1) angular resolution, 2) temporal resolution, 3) light-gathering power, and 4) data-recording convenience. An optical system meeting these four requirements was constructed. With this system, an observing campaign in Fort Smith, Northwest Territories, has begun and images of the small-scale structure of auroral arcs are presented. Are thicknesses of approximately 40 m were observed. These measurements of are thicknesses may provide a critical test for the many theories about the origins of auroral arcs.