Energetic O+ions in the magnetosphere

Observations of energetic heavy ions are reported on seven occasions during three magnetic storms in 1969. The data were acquired from an energetic ion mass spectrometer experiment on satellite 1969-25B. Measurements were made at 1, 3, and 9 keV. Data from an orbit on March 24, 1969, are examined in some detail. The observed heavy ion fluxes are shown to exhibit a morphology similar to that reported by Shelley et al. [1972] for O+ fluxes in the magnetic storm of December 17, 1971, and their identification as O+ ions is made on this basis. The latitude distribution of these ion fluxes is compared to simultaneous satellite and ground-based measurements of other phenomena. In the case examined, the most intense O+ fluxes were found to be located equatorward of the high-latitude boundary of locally mirroring energetic electrons and poleward of a stable auroral red (SAR) arc. They were located on a steep density gradient in the ambient cold plasma at the satellite altitude of 480 km. A comparison of the location of the O+ fluxes on six other occasions with SAR arc observations acquired during the same storms indicates that the low-latitude limit of the O+ is on the average about 1 L unit poleward of the arc.