Fig. 1. EUV spectroscopy of the Io plasma torus (IPT) with EXCEED.
(A) The slit position relative to Jupiter and the IPT. The column of red vertical
boxes shows the location of the slit relative to the disk of Jupiter in the center
and the black dashed ellipse of the IPT. The slit orientation was aligned parallel
to and centered on the IPT latitudinal center during the entire observation
period. Spatial information is available only along the longer axis of the slit
(360 arc sec in total) and provides a resolution of ~0.2RJ. The shorter axis
(10 arc sec in width) corresponds to 0.44RJ. (B) The spectrum of Jupiter and
the IPT, integrated over 550 min. The vertical axis shows the spatial distribution
(bottom corresponds to dawn side); the horizontal axis corresponds to the
spectral distribution. Although the geocoronal background has been subtracted, residue at some bright lines (He I 58.4 nm, H I 121.6 nm, etc.) remains.
At the top, the major spectral features are labeled by approximate wavelength
and responsible ions.
Fig. 2. Absolute brightness–calibrated spectra from radial
distances of 5.9 to 7.6 RJ for both dawn and dusk (black
lines). Spatial bins are summed over 0.4RJ for the spectra
from 5.9 to 7.1 RJ. The outermost bins at 7.6RJ are summed
over 0.8RJ to improve the signal-to-noise ratio. For comparison,
the best-fit model spectra are also shown as red dashed lines on
each spectrum. The shaded areas indicate where geocoronal
emissions (He I 58.4 nm, ghost of Lya 79 nm, O II 83.4 nm, Lyb
102.5 nm, Lya 121.6 nm, O I 130.4 nm, and O I 135.6 nm)
contaminate the data and were not used in the model parameter