Discontinuities in the jovian plasma disk of sulphur and oxygen ions

The process of local acceleration of the plasma cloud freshly ejected from Io into the jovian magnetosphere is considered here. A physical model previously employed to investigate the motion of artificial barium cloud, is used to estimate the time scale for such transient acceleration. In normal conditions, the new ions could be accelerated to full corotation within ∼3 × 10²s of injection. But the corresponding time scale might be increased 10-fold or so at the peaks of mass injection. In this way the observations of non-rigid corotation of the S⁺ ions of sporadic nature may be understood. The temperature and ionization discontinuities in the Io torus as observed by the Voyager experiments is also considered. Here we propose that such a sharp transition is related to the coupling of the radial diffusion and heating plus cooling of the thermal plasma.