If a planetary satellite has an intrinsic dipole field, the drift motion of charged particles will be diverted, by varying degree, around the satellite. It is shown here that, if Io has a dipole field with an equatorial surface field of the order of 2000 nT, both protons and electrons with energies less than 1 MeV will be strongly absorbed, while those with higher energies may not be affected. Furthermore, if the dipole moment of Io is anti-parallel to that of Jupiter, it would be expected that the surface sputtering effect by corotating magnetospheric ions to be most pronounced near the inner and trailing hemispheres, as indicated by some observations of the neutral sodium cloud.