Dust ion-acoustic dromions in Saturn's magnetosphere

Abstract

Motivated by observations of localized electrostatic wavepackets by the Cassini and (earlier) by Voyager 1 and 2 mission(s) in Saturn's magnetosphere, we have investigated the existence conditions and the dynamical evolution of localized multi-dimensional structures in the Saturnian dusty plasma environment. To this effect, we have adopted a plasma-fluid model for dust-ion acoustic (DIA) excitations, taking into account the presence of a highly energetic (suprathermal, kappa-distributed) electron population in combination with massive dust particulates in the background. A multiple scales perturbation method was shown to lead to a Davey-Stewartson (DS) system of evolution equations, if one assumes perpendicular carrier wave propagation across the magnetic field (direction). The system is then shown to possess two regimes mainly, known in the literature as DS-I and DS-II. In the former case, if certain conditions are fulfilled, exponentially localized solutions are obtained, known as dromions. The combined effects of various physical parameters such as the electron spectral index, the ambient magnetic field (strength), and the dust concentration have been examined. A numerical investigation reveals that the dromion amplitude increases with higher dust concentration, while it decreases for lower $\kappa_e$ (i.e. with an increase in the suprathermal electron population component). A stronger magnetic field results in higher amplitude but narrower dromions. Our results provide a comprehensive framework for modeling modulated electrostatic wavepackets, in direct comparison with experimental data in planetary environments, in Saturn's magnetosphere, and elsewhere.