A global map of average electron densities in the magnetosphere of Saturn

Measurements from the Cassini Radio and Plasma Wave Science (RPWS) experiment obtained during the entire orbital phase of the Cassini mission around Saturn (13.2 years) are processed into a meridional map of plasma densities, comprising the innermost region of the ring ionosphere, the Enceladus plasma torus, and the outer magnetosphere, up to a dipole L-shell of 30. We combine data from RPWS wave observations, such as whistler-mode waves and upper hybrid electrostatic emissions, and from the RPWS Langmuir probe when operated in the proxy mode, providing an estimate for the spacecraft floating potential. In the region between dipole L-shells of 2.4 and 30, observed electron densities are described by an analytic model that fits two functions, one for the water group ions and one for the protons, to observed densities across latitude on each magnetic field line. The derived electron density profiles are then augmented by a model for the cold core electron temperature as a function of L-shell to obtain a meridional map of the electrostatic potential of the ambipolar electric field. The potential is extrapolated to the inner region of the rings, i.e., to below L = 2.4, to solve for the distribution of electron density in the ring ionosphere. A solution is based on a diffusive equilibrium model for the electrons and two ion species, and on observations from Cassini along the Saturn Orbit Insertion (SOI) trajectory. A combination of analytic and diffusive equilibrium results finally yields an average global picture for the distribution of electron density in Saturn’s magnetosphere. The global density model is provided as the NASA CDF (Common Data Format). The CDF format is a self-describing data standard, with all metadata, variable definitions, and data structures embedded. The core data variable enabling detailed spatial mapping of electron density across Saturn’s magnetosphere, Density_L_Lat, represents the electron density as a function of both L-shell (a measure of magnetic field line distance at the planet's equatorial plane in Saturn radii, Rs =60268 km) and latitude in Kronocentric coordinates, with values given in cm⁻³. Additional key variables include Potential, which represents the electric potential from the ambipolar electric field in Volts; Electron_temperature, describing the cold core electron temperature in electronvolts; and H_scale, the electron scale height in Saturn radii, indicating the vertical extent of the electron population. The Omega variable provides the plasma corotation rate, assuming the strict corotation with a period of 10.66 hours.