Modeling Jupiter’s Ionosphere: Reproduction of Global H3+ Density Maps, and Electron Density Profiles from Galileo and Juno

We present the Jovian Atmospheric Model Making Ionospheric EStimates (JAMMIES), a new model for Jupiter's non-auroral ionosphere. JAMMIES is a 2D model of Jupiter’s non-auroral ionosphere that solves the ion continuity and momentum equations in a dipole coordinate system. It was recently adapted from SAMI2 (Huba+2000), a model that has successfully reproduced numerous ionospheric features on Earth. JAMMIES incorporates neutral atmospheric inputs from a new general circulation model, JTIM (Mueller-Wodarg+2024), and defines its grid based on the updated JRM33 magnetic field model (Connerney+2022). JAMMIES is able to reproduce structures globally in H₃⁺ column density co-located with the long unexplained H₃⁺ Dark Ribbon: a lack of emission from the dominant molecular ion — H₃⁺ — coincident with Jupiter’s magnetic equator (Stallard+2018). We present how JAMMIES is able to recreate this ionospheric feature via Earth-like interhemispheric electrodynamic transport or neutral-wind driven-motion along magnetic field lines. We also present how we use JAMMIES to model electron density altitude profiles measured at dawn and dusk from radio occultations using the Galileo and Juno spacecrafts. Electron density altitude profiles from radio occultations are highly variable with no obvious systematic trends (Mendillo+2022). We find that much of that variability is captured in JAMMIES as a result of wind-driven field aligned plasma transport. Neutral winds from JTIM have strong westward zonal components and converge towards the equator. When combined with Jupiter’s complex magnetic geometry, this results in irregular patterns of effective upward and downward plasma transport, which are broadly consistent with observed plasma distributions. Additional modifications follow from vertical plasma drifts arising from electrodynamic interactions near the magnetic equator. The fact that plasma dynamics driven by a single neutral wind pattern can reproduce radio occultation morphologies from both the Galileo and Juno eras (spanning 30 years) suggests that Jupiter’s ionosphere is remarkably stable. Future JAMMIES simulations will further investigate this stability through comparisons with additional datasets and will enhance modeling capabilities by incorporating expanded chemistry and self-consistent plasma temperature calculations.