Polar wind outflow model: Saturn results

摘要

The Saturnian system's configuration and dynamics are to a large extent controlled by the planet's rapid rotation and the plasma in the magnetosphere. Therefore characterizing the relative importance of the various plasma sources is crucial to understanding Saturn's magnetosphere. Most research in this area focuses on the addition of mass from the icy satellites, the rings, and Titan, while comparatively little attention has been paid to the ionospheric source. We investigate the ionospheric source at high latitude using multifluid numerical simulations of Saturn's polar wind and find that the magnitude of the particle source rate out of the polar cap is between 2.1 × 10~(26) and 7.5 × 10~(27) s~(-1). Our multifluid simulations are carried out using the Polar Wind Outflow Model (PWOM). This new model is capable of calculating the polar wind at Earth and Saturn by solving the gyrotropic transport equations. The polar wind at Saturn is modeled from below the peak ionospheric density to an altitude of one Saturn radius, yielding fluxes for H_3~+, H~+, and electrons. Because the neutral temperature is ill constrained, we calculate source rates for various Saturnian atmospheric profiles corresponding to neutral temperatures of 420, 600, 800, 1000, 1500 K. We compare the results with those calculated from other models and measurements where appropriate.