Abstract: | Low-resolution spectra of the Io plasma torus have been obtained on 10 and 11 February 1992 (2 days after the Ulysses encounter) using the 2 m telescope of the Bulgarian National Observatory. The spectra show the forbidden line emissions of S+ (λλ 6716, 6731 Å) and S2+ (λ 6312 Å). Measured intensities are compared with a Voyager-type model. The intensity distribution of [SII] is found to deviate from the model predictions which indicates a change in the torus at the Ulysses encounter when compared with the Voyager epoch. A corotating structure was observed, both in [SII] and [SIII], at λIII = 170°, showing that the torus was not azimuthally symmetric. The λ 6716/λ 6731 and λ 6731/ λ 6312 line ratios indicate a higher electron density at the time of the Ulysses observations. Additionally, the shift of the torus caused by the dawn-dusk electric field could be observed. Peak intensities in [SII] were found at 5.66 ± 0.02 RJ on the West ansa and 5.91 ± 0.04 RJ on the East. |