Altitude Effects in the Red Part of the Auroral Spectrum and the Two Types of Red Auroras

Abstract

IN a previous note in NATURE1, I described observations made at Oslo of an auroral display which showed red upper limits, while the lower part had the ordinary greenish-yellow colour. Spectroscopic observations gave an enormous enhancement of the red oxygen line 6300 with increasing height. In a later paper2, I described quantitative measurements of spectrograms corresponding to auroras of ordinary colour, which also gave a considerable enhancement of the red line 6300 with increasing altitude. It became a matter of importance to make further measurements in order to see if the altitude effect on the red line was a general occurrence.