Survey of Ion Properties in Jupiter's Plasma Sheet: Juno JADE‐I Observations. Issue 4 (14th April 2020)

• Record Type: Journal Article
• Authors: Kim, Thomas K.; Ebert, R. W.; Valek, P. W.; Allegrini, F.; McComas, D. J.; Bagenal, F.; Connerney, J. E. P.; Livadiotis, G.; Thomsen, M. F.; Wilson, R. J.; Bolton, S. J.
• Is Part Of: Journal of geophysical research. Volume 125:Issue 4(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-04-14
• Subjects: Jupiter -- ion composition -- plasma sheet -- ion plasma parameters; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2019JA027696
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: 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 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 +, 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 ΣO n+ to ΣS n+ 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. Plain Language Summary: The Jovian Auroral Distributions Experiment (JADE) on Juno has continuously investigated the plasma environment in Jupiter's magnetosphere since its arrival in August 2016. The polar‐orbiting spacecraft enables JADE to explore both equatorial and off‐equator regions of Jupiter's plasma sheet. In this study, we present plasma sheet ion characteristics such as ion composition, flow speed, and temperatures for H +, O +, O 2+, O 3+, Na +, S +, S 2+, and S 3+ that are originating from the innermost Galilean satellite Io. Spatial dependence of ion characteristics is discussed and compared to previous observations. While the density profiles agree well with the Voyager‐based studies, temperatures found in this study show at least an order of magnitude higher values. A new addition to this paper is that the latitudinal distribution of ions shows a trend in the mass. The relative composition of protons increases compared to the heavier ions in the off‐equator regions. These observations provide insights on how the ions are distributed throughout Jupiter's magnetosphere and improve our current understanding of ion dynamics in the plasma sheet. Key Points: Ion flow speed, number density, temperature, and composition in Jupiter's plasma sheet show radial and/or latitudinal trends H +, O +, and S 2+ are the primary ions, the contribution of H + and S 2+ increasing and decreasing, respectively, in the off‐equator region The O + to S 2+ density ratio is variable, the 5 RJ bin averages ranging from 0.7–1.5 (equator) and 1.1–1.8 (off‐equator)