A new pathway of Saturnian ring-ionosphere coupling via charged nanograins

From a re-examination of the trajectories of small charged grains in the vicinity of the Saturnian rings, it is shown that the orbital motion of positively charged grains with a charge-to-mass ratio on the order of 10^–6 e amu^–1 could allow the injection of water material into the equatorial atmosphere. Thus, a mechanism of ionospheric depletion in the equatorial region is provided, as indicated by the Cassini radio occultation measurements.