SPECTROSCOPY OF THE EXTREME ULTRAVIOLET DAYGLOW AT 6.5A RESOLUTION - ATOMIC AND IONIC EMISSIONS BETWEEN 530 AND 1240A

EUV spectra (530‐1500Å) of the day airglow in up, down and horizontal aspect orientations have been obtained with 6.5Å resolution and a limiting sensitivity of 5R from a rocket experiment. Below 834Å the spectrum is rich in previously unobserved OII transitions connecting with 4So, ²Do, and ²Po states. Recent broad‐band photometric observations of geocoronal HeI 584Å emission can be understood in terms of the newly observed OII emissions. The OI 989Å and OI 1304Å emissions exhibit similar dependence on altitude and viewing geometry with the OI 989Å brightness 1/15 that of OI 1304. Emission at 1026Å is identified as geocoronal HI Lyman‐β rather than OI multiplet emission and observed intensities agree well with model estimates. An unexpectedly high NI 1200/NI 1134Å brightness ratio is evidence of a significant contribution from photodissociative excitation of N2 to the NI 1200Å source function. Copyright 1979 by the American Geophysical Union.