Nonlinear dust-acoustic wave dynamics in nonthermal Saturnian E-ring with negative ion moderation

Abstract

The nonlinear stability dynamics of dust-acoustic waves (DAWs) near the plasma-active satellite of Saturn, Enceladus, is herein theoretically investigated in the perturbative framework. Enceladus being the source of the materials of Saturn's one of the most diffuse and wide E-ring, has a very active plasma environment rich in diversified collective dynamics of freedom. This theoretical model formalism is developed in the light of observations made by the Radio and Plasma Wave Science (RPWS) instrument inbuilt in the Cassini spacecraft in the vicinity of Enceladus. The model consists of electrons, positive ions, and negative ions obeying nonthermal kappa distribution laws. In contrast, the constitutive massive charged dust grains are treated as inviscid fluid. A standard method of multiple scaling technique is systematically employed to yield a Korteweg-de Vries (KdV) equation on the first-order electrostatic potential fluctuations. A constructed numerical platform demonstrates that such fluctuations evolve as a solitary pulse-train or solitary wave chain of rarefactive type. The results are further compared with solitary structures detected by RPWS during Cassini's closest approach to Enceladus. It is interestingly found that the bipolar electrostatic field amplitude of the derived dust-acoustic solitary pulses (4−11 mV/m) theoretically investigated here falls well within the range of observationally obtained field value (≥10 mV/m). Finally, the non-trivial wave amplitude growth features with diverse plasma multi-parametric variations are spotlighted illustratively.