Publication Date:
2019
Description:
Abstract
The Jovian Auroral Distributions Experiment Ion sensor (JADE‐I) on Juno is a plasma instrument that measures the energy‐per‐charge (E/Q) distribution of 0.01 to 46.2 keV/q ions over a mass‐per‐charge (M/Q) range of 1 – 64 amu/q. However, distinguishing O+ and S2+ from JADE‐I's measurements is a challenging task due to similarities in their M/Q (≈ 16 amu/q). Because of this, O+ and S2+ have not been fully resolved in the in‐situ measurements made by plasma instruments at Jupiter (e.g., Voyager PLS and Galileo PLS) and their relative ratios has been studied using physical chemistry models and UV remote observations. To resolve this ambiguity, a ray‐tracing simulation combined with carbon foil effects is developed and used to obtain instrument response functions for H+, O+, O2+, O3+, Na+, S+, S2+, and S3+. The simulation results indicate that JADE‐I can resolve the $M/Q$ ambiguity between O+ and S2+ due to a significant difference in their charge state modification process and a presence of a large electric potential difference (≈ 8 kV) between its carbon foils and MCPs. A forward model based on instrument response functions and eight convected kappa distributions is then used to obtain ion properties at the equatorial plasma sheet (≈ 36 jovian radii) in the pre‐dawn sector of magnetosphere. The number density ratio between O+ and S2+ for the selected plasma sheet crossings ranges from 0.2 to 0.7 (mean value 0.37 ± 0.12) and the number density ratio between total oxygen ions to total sulfur ions ranges from 0.2 to 0.6 (0.41 ±0.09).
Print ISSN:
2169-9380
Electronic ISSN:
2169-9402
Topics:
Geosciences
,
Physics
