The extreme ultraviolet (750‐1230 A) spectrum of an aurora

Extreme ultraviolet auroral spectra have been obtained in the wavelength range of 750‐1230 A resolution with a rocket‐borne grating spectrometer. Atomic emissions of NI, NII, OI and OII are the dominant features along with geocoronal HI Lyman α. N 2 emission bands, which appear strongly in laboratory electron impact spectra, appear only as a modest background continuum between 900 to 1100 A. The observed intensities are consistent with electron impact excitation of O and N 2 . For optically thick emissions, such as NI λ1200, radiation transport along the arc results in an intensity enhancement when viewed through the arc towards the zenith.