Re-Analysis of the Cassini RPWS/LP Data in Titan's Ionosphere: 1. Detection of Several Electron Populations

TL;DR

This study re-analyzed Cassini RPWS/LP data from Titan's ionosphere, revealing multiple electron populations influenced by various physical processes, which helps improve understanding of Titan's plasma environment.

Contribution

Introduces a new analysis method to identify multiple electron populations in Titan's ionosphere using Cassini data, enhancing interpretation of plasma measurements.

Findings

Identification of 2 to 4 distinct electron populations

Variation of populations with solar illumination and altitude

Attribution of populations to photo-ionization, magnetospheric particles, dusty plasma, and probe emission

Abstract

Current models of Titan ionosphere have difficulties in explaining the observed electron density and/or temperature. In order to get new insights, we re-analyzed the data taken in the ionosphere of Titan by the Cassini Langmuir probe (LP), part of the Radio and Plasma Wave Science (RPWS) instrument. This is the first of two papers that present the new analysis method (current paper) and statistics on the whole dataset. We suggest that between 2 and 4 electron populations are necessary to fit the data. Each population is defined by a potential, an electron density and an electron temperature and is easily visualized by a dinstinct peak in the second derivative of the electron current, which is physically related to the electron energy distribution function (Druyvesteyn method). The detected populations vary with solar illumination and altitude. We suggest that the 4 electron populations are due to photo-ionization, magnetospheric particles, dusty plasma and electron emission from the probe boom, respectively.