The EUV dayglow at high spectral resolution

Abstract

Rocket observations of the dayglow spectrum of the terrestrial atmosphere between 840 Å and 1860 Å at 2 Å resolution were obtained with a sounding rocket payload flown on January 17, 1985. Additionally, spectra were also obtained using a 0.125‐m focal length scanning Ebert‐Fastie monochromator covering the wavelength interval of 1150–1550 Å at 7 Å resolution on this flight and on a sounding rocket flight on August 29, 1983, under similar viewing geometries and solar zenith angles. Three bands of the N 2 c ′ 4 system are seen clearly resolved in the dayglow. Analysis of high‐resolution N 2 Lyman‐Birge‐Hopfield data shows no anomalous vibrational distribution as has been reported from other observations. The altitude profiles of the observed O and N 2 emissions demonstrate that the MSIS‐83 model O and N 2 densities are appropriate for the conditions of both the 1983 and 1985 rocket flights. A reduction of a factor of 2 in the model O 2 density is required for both flights to reproduce the low‐altitude atomic oxygen emission profiles. The volume excitation rates calculated using the Hinteregger et al. (1981) SC#21REFW solar reference spectrum and the photoelectron flux model of Strickland and Meier (1982) need to be scaled upward by a factor of 1.4 for both flights to match the observations.