Characteristics of charged dust inferred from the Cassini RPWS measurements in the vicinity of Enceladus

The data obtained by the Cassini Radio and Plasma Wave Science (RPWS) instrument during the shallow (17.02.2005) and the steep (14.07.2005) crossings of the E-ring revealed a considerable electron depletion in proximity to Enceladus's orbit (the difference between the ion and electron densities can reach ∼70cm-3). Assuming that this depletion is a signature of the presence of charged dust particles, the main characteristics of dust down to submicron   sized particles are derived. The differential size distribution is found to be well described by a power law with an index μ∼5.5–6μ∼5.5–6 for the lower size limit amin=0.03μm and μ∼7.3–8μ∼7.3–8 for amin=0.1μm. The calculated average integral dust number density is weakly affected by values of μμ and aminamin. For a≳0.1μm, both flybys gave the maximum dust density about 0.1–0.3cm-3 in the vicinity of Enceladus. Our results imply that the dust structure near Enceladus is characterized by approximately the same vertical length scale of 8000 km and reaches a maximum at the same radial distance (displaced outward of the orbit of Enceladus) as found by Kempf et al. [2008. The E-ring in the vicinity of Enceladus. Spatial distribution and properties of the ring particles. Icarus 193, 420–437], from the dust impact data.