  With the laws of mass conservation, momentum conservation and energy
conservation, incorporating the processes of neutral gas ionization and ion
diffusion, we develop a self-consistent model for the bright ribbon --- the
most prominent feature in Io's plasma torus. The model parameters are well
constrained by earlier {\it in situ} observations with the Galileo and Voyager
spacescrafts. Our model calculation indicates that the total power dissipated
inside the torus is 3.6 times bigger than the total power transported to Jovian
ionosphere via Birkeland current. The power dissipation inside the torus is
relatively uniform. Most of the power transportation associated with the
Birkeland current, however, is localized near the flux tube of Io. With a
height-intergrated conductivity of 0.15$\,$mho in Jovian ionosphere, consistent
with earlier aeronomy models, the model gives a reasonable fit to the recent
observations of the FUV Io tail on Jupiter. Extra mass loading near Io is
required in the model. This excess of mass injection into the plasma torus may
explain the Io-correlated energy source revealed by earlier EUV observations
with the Voyager spacecrafts. Further investigation of the model implications
is warranted.
