An expanded magnetospheric electron density model for Saturn in the post-Cassini era

The Radio and Plasma Wave Science (RPWS) experiment onboard the Cassini spacecraft collected electron density data in Saturn's magnetosphere during the entire orbital phase of the mission, comprising over 13 years of data. Electron densities have been derived from observations of electromagnetic and plasma waves, like whistler-mode hiss and electrostatic upper hybrid emissions, and also from a Langmuir probe, which measures the spacecraft potential as a proxy to the electron density in a thin plasma region. The method based on wave observations has a good coverage of high densities exceeding 1 cm-3 in the Enceladus plasma torus, whereas Langmuir probe proxy data cover regions with lower densities well. Both datasets are combined in the present study and fit by an analytic model that establishes charge neutrality between the electrons and two ion species in the form of hydrogen (protons) and water group ions. The fitting is based on bin-averages across all local times and both latitudinal hemispheres, and it spans between dipole L-shells of 2.4 and 30. Electron densities in the ring ionosphere at L < 2.4 are reconstructed from the modeled potential of the ambipolar electric field and a simplified diffusive equilibrium between electrons and a single ion species.