Origin and energetics of the Io plasma torus

The ionization of the gas ejections from the Io satellite into the Jovian magnetosphere by the corotating magnetospheric plasma flow is considered. It is shown that the plasma flow velocity at the Io orbit exceeds the critical velocity at which the anomalous electron ionization of the heavy gas components takes place due to collisionless energy transfer from ionized gas atoms to plasma electrons. The energy, number density and spatial distribution of suprathermal electrons is calculated using the quasilinear theory of newly ionized atoms instability in a moving plasma. Saturation of the plasma density build up in a plasma is considered in terms of the instability quenching by Coulomb collisions.