The lo sulfur torus in 1981

A Fabry-Perot/CCD spectrometer was used to obtain images of the Io torus in emission lines of [S II] λ6716, λ6731 and [S III] λ9531 in 1981 February and March on the 2.1-m telescope at KPNO. The [S II] and [S III] images showed a large variation in brightness and radial extent. There is an indication that [S II] and [S III] emissions in the warm torus are correlated. The [S II] and [S III] emissions in the warm torus also have similar scale heights along the magnetic field lines of ∼ 0.6 R_J-0.72 R_J. The east-west asymmetry in the [S II] images taken at similar magnetic longitudes, but 2.5 Jovian rotations apart, supports the theory of convective motions suggested by others. In addition to the images, simultaneous measurements of the [S II] λ6731 line profile were made on one night using a Fabry-Perot scanning spectrometer on the 4-m telescope at KPNO. The [S II] spectral scans implied ion temperatures perpendicular to the magnetic field of (52 ± 10) × 10 ³ K at 5.2 R_J to 5.6 R_J from Jupiter and a temperature greater than 3 × 10 ⁵ K at 6 R_J from Jupiter.