The UV auroral distribution: Its impulsive nature

Abstract

The UV Imager on the Swedish Viking satellite obtained near-instantaneous (1 second exposure) spatial distributions of the entire Northern Hemisphere aurora. The short exposure time coupled with a repetition rate as rapid as three images per minute permitted scientists to observe rapid variations of the aurora in space and time. Numerous examples of impulsive changes were recorded during the 1986 emission, and many of these were of a sufficient scale that they can be expected to affect the high latitude thermosphere. Such events are not uncommon and thus present a difficult challenge for global thermospheric modelers who desire realistic auroral input parameters for their models. One important aspect is the contribution of auroral energy input not only on the nightside due to substorm effects, but impulsive events on the dayside as well. The purpose of this paper is to acquaint scientists with the dramatic variations observed by presenting selected examples of the image data.