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

Abstract

AbstractThis 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 RJ in the dawn to midnight sector of Jupiter's magnetosphere. The survey covers Juno orbits 5–22, and the observations are separated by equatorial (|zmag[RJ]| ≤ 1.5) and off‐equator (|zmag[RJ]|>1.5) regions. Plasma parameters for H+, O+, O2+, O3+, Na+, S+, S2+, and S3+ 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 S2+ 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 S2+. The relative contribution of H+ and S2+ increases and decreases, respectively, in the off‐equator regions, supporting the interpretation that the latitudinal distribution of ions is mass dependent. The O+ to S2+ and ΣOn+ to ΣSn+ number density ratios are variable, the 5 RJ bin averages for O+ to S2+ ranging from ∼0.75–1.5 (equator) and ∼1.1–1.8 (off‐equator) and ΣOn+ to ΣSn+ 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.