Chynna Spitler

The Juno mission has elucidated magnetosphere processes, structure, and dynamics via multi‐instrument plasma and magnetic field observations. In this study, these instruments are used to identify magnetic reconnection during the Juno extended mission from a survey of 490 magnetopause crossings at the mid‐latitude southern dusk magnetopause. This survey spans distances of 30–99 R _J , 14–20 local time, and 30°–65° in southern latitude. We identify reconnection outflow jets, plasma heating, and Hall magnetic fields as reconnection signatures while independently applying the Swisdak and Walén relations to each magnetopause crossing. Additionally, eastward versus westward interplanetary magnetic field (IMF) conditions are compared in this context. The results show that magnetic reconnection is most likely to occur during eastward IMF at the mid‐latitude dusk magnetopause due to favorable magnetic shear conditions. The identified eastward IMF reconnection events strongly adhere to the Walén relation, showing signatures of Alfvénic flow perturbations.

The Juno mission, in conjunction with past missions and Earth‐based observations, has provided a wealth of information on Jupiter's magnetosphere. This magnetosphere is governed by Jupiter's strong magnetic field, rapid 10‐hr rotation, and a significant internal plasma source, the volcanic moon Io. Jupiter's magnetodisc exhibits plasma temperatures that deviate strongly from adiabatic expectations, increasing by nearly two orders of magnitude between the Io plasma torus and ∼25 . The physical mechanisms responsible for this heating remain poorly understood, particularly in the middle magnetosphere where advective transport dominates. In this study, we use a global magnetohydrodynamic (MHD) simulation to investigate the processes controlling plasma temperature evolution. Fluid tracing and test particle simulations are performed to analyze radial transport and energization within the magnetodisc. Our results reproduce key features of the observed temperature profiles, including the pronounced increase beyond 10 , without the need for additional heating terms. We demonstrate that a combination of tail reconnection, adiabatic compression, and large‐scale radial and corotational transport can explain the simulated temperature profiles, providing insight into the mechanisms governing plasma heating in Jupiter's magnetodisc. These findings highlight the importance of global scale MHD processes in shaping the thermal structure of the middle magnetosphere and offer a framework for interpreting Juno observations in regions not directly observed.

The ion temperature in Jupiter's middle magnetosphere has been known to stay constant (or even increase) as a function of radial distance from the planet. This suggests that there is a non‐adiabatic heating process occurring in this region. Efforts have been made to explain this heating with different turbulent heating models utilizing data from previous science missions to Jupiter (Ng et al., 2018, https://doi.org/10.1029/2018JA025345 ; 2022, https://doi.org/10.1029/2021GL096662 ; Saur, 2004, https://doi.org/10.1086/382588 ). Using the turbulent heating rate density calculated from the Juno spacecraft magnetometer and particle data based on a forward fitting model utilizing a kappa distribution (Wang, Bagenal, Wilson, Nerney, et al., 2024, https://doi.org/10.1029/2023JA032218 ; Wang et al., 2024b, https://doi.org/10.1029/2024JA033454 ), the thermal equilibrium ion temperature in Jupiter's middle magnetosphere is estimated using an advection temperature model. We find that the model is not sufficient to account for the – K ( keV) temperatures seen in the forward fits particle data, which is about an order of magnitude higher than previously reported in particle data surveys (Bagenal & Delamere, 2011, https://doi.org/10.1029/2010JA016294 ).

In Jupiter's magnetosphere, the outward transport of Io‐genic plasma and the planetward injection of energetic particles are facilitated by flux tube interchange motion driven by centrifugal instabilities. Flux tube content and entropy are two competing key quantities that determine the behavior of the system. In this study, we first review the centrifugal force driven dynamics in different regions. Benefiting from Juno's high‐quality in situ data in the off‐equatorial region, we then analyze the flux tube integrals and interchange instability criteria between M‐shells 13 and 40 using numerical integration. On average, the entropy term dominates the system, resulting in a generally stable system for interchange motion. Finally, we investigate an injection event, in which predictions from the criteria align with the observed flow direction. This study illustrates the overall stability of the system with small‐scale, intermittent dynamic phenomena.

Jupiter's rapidly rotating magnetosphere, with internal plasma sources such as the volcanic moon Io, provides a unique natural laboratory for studying internally driven planetary magnetospheres. Using the Grid Agnostic Magnetohydrodynamics for Extended Research Applications (GAMERA) model, we simulated Jupiter's magnetosphere with variable ionospheric Pedersen conductances, which is mainly responsible for energy dissipation between the ionosphere and magnetosphere though convection. We chose values ranging from 0.5 to mho to investigate the Pedersen conductance's role in controlling mid‐magnetosphere region's dynamics and the closing of magnetosphere‐ionosphere currents. Simulated density, temperature, and radial and azimuthal flows in the equator are compared with observations from the Jovian Auroral Distributions Experiment (JADE) on the Juno spacecraft. All simulation cases exhibit dawn‐dusk asymmetries, in both the ionosphere and magnetosphere. The 0.5 case showed the best agreement with JADE observations, while the 1 case exhibited a magnetic topology more consistent with the auroral observations from the Hubble Space Telescope and Juno. These results enhance our understanding of Jupiter's magnetosphere‐ionosphere coupling, provide context for observations, and inform the background parameters of future test particle simulations and data‐model comparisons using the GAMERA model.

In Jupiter's magnetosphere, the outward transport of Io-genic plasma and the planetward injection of energetic particles are facilitated by flux tube interchange motion driven by centrifugal instabilities. Flux tube content and entropy are two competing key quantities that determine the behavior of the system. In this study, we first review the centrifugal force driven dynamics in different regions. Benefiting from Juno's high-quality in-situ data in the off-equatorial region, we then analyze the flux tube integrals and interchange instability criteria between M-shells 13 and 40 using numerical integration. On average, the entropy term dominates the system, resulting in a generally stable system for interchange motion. Finally, we investigate an injection event, in which predictions from the criteria align with the observed flow direction. This study illustrates the overall stability of the system with small-scale, intermittent dynamic phenomena.

Jupiter's magnetosphere exhibits notable distinctions from the terrestrial magnetosphere. The structure and dynamics of Jupiter's dawnside magnetosphere can be characterized as a competition between internally driven sunward flow and solar wind‐driven tailward flow. During the prime mission, Juno acquired extensive data from dawn to midnight, sampling the magnetodisc and higher latitude regions. Numerical moments from the Jovian Auroral Distributions Experiment (JADE‐I) plasma (ion) instrument revealed a mid‐latitude region of anticorotational (−v_ϕ) flow. While the magnitude of the flow is subject to uncertainty due to low count rates in these rarefied regions, we demonstrate in the raw JADE‐I data that the sign of v_ϕ is a robust measurement. Global Grid Agnostic Magnetohydrodyamics for Extended Research Applications simulations show a similar region of strongly reduced flow in proximity to open field lines. Additionally, we use Jupiter Energetic‐particle Detector Instrument integral moments to determine the Heⁿ⁺/H⁺ ratio (where n refers to He⁺ or He⁺⁺) and show that a transition to solar wind‐like composition occurs in the same region as the anticorotational flow. We conclude that the global simulations are consistent with the Juno data, where the simulations show a crescent of open magnetic flux that is bounded by the magnetodisc and a closed high‐latitude polar region (nominally the polar cap), which is never observed in the terrestrial magnetosphere. The distinct distribution of open flux in Jupiter's dawnside magnetosphere suggests the significance of planetary rotation and may represent a characteristic feature of rotating giant magnetospheres for future exploration.

Sudden Impulse (SI) events and Sudden Storm Commencements (SSC) are rapid geomagnetic variations associated with a compression of the magnetic field. Starting in 2006 Ebre Observatory, the IAGA international database on rapid magnetic variations, began to differentiate SI events from SSCs. These events have different magnetic characteristics depending on local time and latitude. Starting in 2006 and ending with the last definitive published dataset, the module SeaPy within Python is used to perform a superposed epoch analysis on SI events and SSCs for high latitude stations and low latitude stations. In relation to low latitude station onset times, we find systematic behavior of the total field strength and North-South component of the magnetic field at high latitudes. Specifically, the SI and SSC signatures are delayed and the compression signature can be highly variable from event to event.