The excitation of Io's atmosphere by Galileo-observed magnetically field-al
igned energetic (0.1-100 keV) electrons have been studied using a Monte Car
lo model. The calculated OI and SI FUV emissions are compared with HST-STIS
observations. It is found that Galileo EPD-observed 15-100 keV electron be
ams are an insignificant source of OI and SI emissions on Io since they are
too energetic to be degraded in Io's atmosphere. We show that Galileo PLS-
observed field-aligned 0.1-5 keV electron fluxes can explain the HST-observ
ed S and O FUV brightness provided a fraction of these electrons precipitat
e into Io's atmosphere. The absorption of FUV emissions by SO2 is found to
be less than 10%. From the qualitative scenario of a correlation between Jo
vian FUV emissions from IFT footprint and Io's FUV emissions we suggest a d
ual role of field-aligned IFT electrons in producing emissions at Io and Ju
piter.