A survey of small-scale spatially periodic distortions of auroral forms

High-resolution television observations by the University of Calgary portable auroral imager of the small-scale spatially periodic distortions of auroral forms known as "curls" are presented. During winter 1995 and 1997 field trips to Rabbit Lake, Saskatchewan, Canada, a large amount of video data containing auroral curls was acquired. Analysis of this data set has led to much improved insight into the properties of these features. Observed spatial and temporal characteristics are presented, with results compared to those of earlier surveys wherever applicable. Striking parallels between the characteristics of these similar to 1 km scale size curls and the characteristics of the similar to 100 km scale size auroral "spirals" observed by the Freja UV imager are pointed out and discussed in terms of shear-driven instabilities. In addition, observations of the interesting new phenomena of "auroral kinks" and "spinning auroral patches" are briefly described.