Survey of Ion Properties in Jupiter's Plasma Sheet: Juno JADE-I Observations

摘要

This study presents a survey of ion flow speed, density, temperature, and composition observed by the Jovian Auroral Distributions Experiment Ion (JADE-I) sensor on Juno from 10-40 R_J in the dawn to midnight sector of Jupiter's magnetosphere. The survey covers Juno orbits 5-22, and the observations are separated by equatorial (|z_(mag)[R_J]| ≤ 1.5) and off-equator (|z_(mag)[R_J]| > 1.5) regions. Plasma parameters for H~+, O~+, O~(2+), O~(3+), Na~+, S~+, S~(2+), and S~(3+) are derived by forward modeling JADE-I's energy-per-charge versus time-of-flight spectra using omni-directional averaged convected kappa distributions and modeled instrument responses. O~+ and S~(2+) are resolved via a ray-tracing simulation based on carbon-foil effects. The ion flow speed increases with radial distance and is comparable to rigid corotation speed out to ～20 RJ. Ion number densities decrease with radial distance, the primary species being H~+, O~+, and S~(2+). The relative contribution of H~+ and S~(2+) increases and decreases, respectively, in the off-equator regions, supporting the interpretation that the latitudinal distribution of ions is mass dependent. The O~+ to S~(2+) and ΣOn+ to ΣSn+ number density ratios are variable, the 5 RJ bin averages for O~+ to S~(2+) ranging from ～0.75-1.5 (equator) and ～1.1-1.8 (off-equator) and ΣO~(n+) to ΣS~(n+) from ～0.6-0.9 (equator) and ～0.8-1.1 (off-equator). Both proton and heavy ion temperatures show order of magnitude increases between 10 and 20 RJ and range from ～100 eV to 10 keV and 1 keV to a few tens of keV, respectively.