The absorption of test particles is studied analytically for the Jovian satellite Io. Io, being a conductor, perturbs the ambient E and B fields in and near the magnetic flux tube that is connected to it. The work is a development of some very early work by Schulz and Eviatar (1977). This paper extends their analysis not only by including more completely the effects of the dipole geometry of the background fields and by treating all particle pitch angles, but also by not being restricted to the infinite satellite conductivity limit. We also take into account the effect of the perturbation varying in amplitude as it propagates through the Io torus. We show that the total energy surfaces of test particles can be used to understand how the different interaction regimes derived by Schulz and Eviatar arise. The theory also enables estimates of the energy range for each type of interaction to be made and can be applied to interpret particle distributions from Io's L shell. As an example, the electron distribution near Io's flux tube has been examined and features expected from the theory are found to be present. ¿American Geophysical Union 1987