Extreme-ultraviolet emissions from an aurora

Two ultraviolet photometers were flown on a Javelin sounding rocket launched from Fort Churchill, Canada, on February 18, 1970, into a weak auroral breakup. The photometers covered the wavelength bands 300–1000 A and 1050–1500 A and observed the aurora while the rocket was above the emitting regions. The observed radiations were found to originate from the visible and X-ray auroral forms recorded by ground-based all-sky cameras and on-board gas proportional X-ray counters. The intensities in the 1050- to 1500-A band were compatible with previous experimental data and available theoretical intensity calculations. The determination of the emitted intensities in the 300- to 1000-A band was hampered by the uncertainties about the wavelength of the radiations being observed, but, if electron excitation of the molecular nitrogen bands at approximately 900 A is assumed to be the dominant mechanism, intensities of up to 150 kR were recorded. Alternate mechanisms considered involved an additional source of radiation in the 650- to 750-A range. In this case, the observed signals corresponded to approximately 20–40 kR of 900-A radiation. Evidence that, on one occasion, radiation from an auroral feature exhibited a temporal pulsation at a frequency of ≃10 Hz is presented. This event was correlated with a simultaneous hardening of the particle energy spectrum.