Rotational Structure of the 3914 A. N₂ ⁺ Band in Sunlit Auroræ

Abstract

ON the evenings of September 3 and 4, 1958, striking sunlit auroræ were observed from Saskatoon in the western sky. Although no photographs were taken, there can be no doubt about the nature of these displays because they showed the divided rays with greyish-coloured upper segments as described by Störmer¹, and because of the peculiarities of the spectrum. During each night of the display a plate was obtained with an f/0.8 Schmidt grating spectrograph having a dispersion of 40 A./mm., while a third plate was obtained from the displays of both nights with a large f/0.8 spectrograph having a dispersion of 20 A./mm. They were set to record the spectrum in the 3500–4500 A. region and the lines of sight of the instruments were directed towards the upper parts of the rays.