Spectroscopy of the extreme ultraviolet dayglow at 6.5Å resolution: Atomic and ionic emissions between 530 and 1240Å

EUV spectra (530-1500A) of the day airglow in up, down and horizontal aspect orientations have been obtained with 6.5A resolution and a limiting sensitivity of 5R from a rocket experiment. Below 834A the spectrum is rich in previously unobserved OII transitions connecting with 4S(0), 2D(0), and 2P(0) states. Recent broad-band photometric observations of geocoronal HeI 584A emission in terms of the newly observed OII emissions are shown. The OI 989A and OI 1304A emissions exhibit similar dependence on altitude and viewing geometry with the OI 989A brightness 1/15 that of OI 1340. Emission at 1026A is identified as geocoronal HI Lyman beta rather than OI multiplet emission and observed intensities agree well with model estimates. An unexpectedly high NI 1200/NI 1134A brightness ratio is evidence of a significant contribution from photodissociative excitation of N2 to the NI 1200A source function.

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