Equatorial aurora/airglow in the far ultraviolet

Abstract

Far ultraviolet emissions in the equatorial zone have been detected at altitudes of less than 500 km with an experiment aboard the Ogo 4 polar-orbiting satellite. The occurrence frequency reached a maximum in both late October and early March during the period August 1967 to May 1968. Both maximums occurred near 2130 local time. Low values during June 1968 indicate a strong seasonal dependence. The emissions were seen quite symmetrically in position at 12°–15° on either side of the magnetic dip equator completely encircling the earth. Often, the peak intensity of the emissions was the same north and south of the equator, but in some cases the intensity was three or four times greater on one side than on the other. In rare cases, emission was totally lacking on one side while clearly present on the other. Simultaneous comparisons of ‘quick-look’ scanning spectrometer data of Barth from Ogo 4 show that the emissions are oxygen lines at 1304 and 1356 A. Possible mechanisms for production of these emissions are discussed.