Multispectral observations of auroral rays and curls

Abstract

Two cases of discrete aurora are presented, in which auroral curls and auroral rays, respectively, were seen. The aurora was imaged by two spatially separated imagers with a long-pass filter (mainly sensitive to N2 and N2+ emissions), and another imager with a narrow-band 7325 Å filter (sensitive to forbidden O+ doublet). Also, spectra of the aurora were recorded. Using the multispectral imaging and spectra we find that the curls occurred in aurora caused by precipitation of energetic electrons with a lack of low-energy population, while in the rays both high and low energy precipitation were present simultaneously. These findings are confirmed by the altitude determination from triangulation. Copyright 2005 by the American Geophysical Union.