Signatures of Open Magnetic Flux in Jupiter's Dawnside Magnetotail

• Published in: AGU advances Vol. 5; no. 2
• Main Authors: Delamere, P. A., Wilson, R. J., Wing, S., Smith, A. R., Mino, B., Spitler, C., Damiano, P., Sorathia, K., Sciola, A., Caggiano, J., Johnson, J. R., Ma, X., Bagenal, F., Zhang, B., Allegrini, F., Ebert, R., Clark, G., Brambles, O.
• Format: Journal Article
• Language: English
• Published: Hoboken John Wiley & Sons, Inc 01.04.2024; Wiley
• Subjects: composition; dynamics; Energy; Flow; Fluctuations; Jupiter; Latitude; Magnetic fields; magnetosphere; open flux; Orbits; Polar environments; Sensors; Simulation
• ISSN: 2576-604X; 2576-604X
• DOI: 10.1029/2023AV001111

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 (−vϕ) 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 vϕ 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. Plain Language Summary Jupiter's magnetic field carves out a cavity in the interplanetary space called a magnetosphere. However, Jupiter's magnetosphere is not completely isolated from the influences of the sun's supersonic solar wind—a magnetized ionized gas. Understanding how the solar wind interacts with Jupiter's magnetosphere has been a long‐standing problem and NASA's Juno mission is producing a rich data set to further explore the system. We find with advanced computer simulations that the solar wind is magnetically connected to Jupiter in a very limited region (i.e., a much smaller region compared with Earth). Here we show that the computer simulations compare favorably with Juno data in the dawn to midnight sector of the magnetosphere. The ionized gas on magnetic field lines connected to Jupiter's northern and southern hemispheres rotate with the planet, while ionized gas on field lines that connect to the solar wind move with the solar wind. Key Points Simulated open field lines are confined to a narrow mid‐latitude region Global simulations show that open field lines can be associated with anti‐corotational flows Jovian Auroral Distributions Experiment moments show anticorotational flows and JEDI moments show solar wind‐like composition in the mid‐to high‐latitude region