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

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⁺, O²⁺, O³⁺, Na⁺, S⁺, S²⁺, and S³⁺ are derived by forward modeling JADE-I's energy-per-charge versus time-of-flight spectra using omnidirectional 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 R_J. 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 R_J 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 R_J and range from ∼100 eV to 10 keV and 1 keV to a few tens of keV, respectively.