Dust charging in the Enceladus torus

Abstract

Employing the parameter space, consistent with available Cassini data, dust charging is studied in the near-Enceladus plasma with special focus on the region close to the moon's plume. The emphasis is on the role of dust size distribution and grain density, the electron temperature, fraction of the hot electrons, and multi-ion composition including the effect of newborn, nonthermalized ions. The sensitivity of the grain potential to variations in the ambient plasma parameters and in the radiative conditions is examined. It is shown that a significant reduction of the electrical potential and the charging time in the dust-loaded regions occurs. This can explain the predominance of nanograins with small negative charges ~e in the plume as detected by the Cassini plasma spectrometer during close encounters with Enceladus. The theoretical findings can be of importance for reliable interpretations of the Cassini Langmuir probe measurements.