The aurora of 27 November 1959 at College, Alaska including observations of a high altitude red ARC

Abstract

Spectrophotometric observations on a rare high altitude red auroral arc were obtained at College, Alaska, in the evening of 27 November 1959. Photometric and photographic triangulation yielded a height of about 350 km for the region of maximum luminosity. The arc can be characterized spectroscopically by the OI λλ6300–6364 lines and the N + 2 1 NG bands, other usual auroral emission features being notably absent. Though the hydrogen lines are present, their identification with the red arc is not certain. The maximum intensity of OI λ6300, 66.7 kR, was reached when the arc passed through the magnetic zenith. The arc was approximately aligned with the geomagnetic field and shifted approximately 10° in latitude, north to south, in a time interval of one hour. An intense and active aurora followed the appearance of the red arc and lasted throughout the night, but did not exhibit any unusual features.