Use has been made of the Pioneer 10 and 11 measurements of the Jovian magnetic field, the Io ionospheric electron density profile, the estimate of the Io atmospheric density, and preliminary measurements of the Jovian ionosphere to revise the Io sheath model. This model suggests that plasma sheaths form between the ionospheric plasma moving with Io and the ambient plasma corotating with Jupiter. Potentials across these sheaths could be as high as 580 kV, which is the motional emf across Io's ionosphere. Electrons and ions can be accelerated across these sheaths. The sheaths may exist at the top of the Io ionosphere with characteristic thicknesses of 1/4 km. This model is consistent with the Pioneer observations of >0.15-MeV electrons at the inner edge of Io's L shell and the enhanced number density of low-energy protons at the outer edge. Ion sputtering of the Io surface may explain the presence of atomic hydrogen and sodium in the vicinity of Io. Also, these accelerated particles may be important to the formation of the Io ionosphere. Directed fluxes of 100-keV electrons in the Io flux tube could be as high as 6¿109 el cm-2 s-1. This flux may lead to the decametric radio emissions, Jovian atmospheric heating, and optical and X ray emissions.