Super-solitary and Flat-top Solitary E-field Structures in non-Maxwellian Plasmas - On the Role of Suprathermal Electrons on Electrostatic Solitary Waves in Saturn's Magnetosphere

Kappa distributions are a common occurrence in various space plasma systems, including the solar wind [1], planetary magnetospheres [2-4], the outer heliosphere [5], and the inner heliosheath [6]. Saturn's magnetosphere can be considered as a typical plasma environment characterized by the coexistence of non-Maxwellian electron populations with different kappa indices. The Cassini mission has reported observations of electrostatic solitary waves (ESWs) in Saturn's magnetosphere [7, 8]. ESWs are usually recorded as a symmetric bipolar pulse in the electric field component parallel to the magnetic field. In this work, we have relied on a multi-ion plasma fluid model, in order to investigate the structural and propagation characteristics of ESWs in a non-Maxwellian plasma environment, focusing in particular on the significance of the spectral index (kappa) on electrostatic solitary wave structures in the magnetosphere of Saturn. The suggested theory successfully explains the observed E-field data's morphology. It should provide an important approach to comprehending localised pulses in E-field data obtained during satellite expeditions, which are known to be significant in defining the microphysics of Saturn's magnetosphere.

Acknowlegments: The authors acknowledge financial support from Khalifa University's Space and Planetary Science Center (Abu Dhabi, UAE) - grant No. KU-SPSC-8474000336. IK acknowledges support from KU via project FSU-2021-012 / 8474000352.

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