Detection of Neutral Oxygen and Sulfur Emissions near Io Using IUE
Skinner, T. E.; Feldman, P. D.; Moos, H. W.; Bertaux, J. -L.; Strobel, D. F.; Ballester, G. E.; Summers, M. E.; Festou, M. C.; Lieske, J. H.
United States, France
Abstract
Two very long IUE exposures obtained with precise control of the spacecraft pointing show emissions due to neutral oxygen and sulfur near Io. The emitting region is centered on Io and is less than five Io diameters across. The two spectra obtained near eastern and western elongation in 1986 July and October, respectively, are similar, independent of whether the downstream or upstream side of the torus plasma flow past Io was viewed. If the spectra were produced solely by electron impact on O and S, the effective electron temperature is low (<2 eV), and large O and S densities are required. Electron impact on SO2 could contribute substantially to the observed spectra.