Journal article
Magnetospheric-Ionospheric-Atmospheric Implications From the Juno Flyby of Ganymede
Journal of geophysical research. Planets, Vol.129(4), e2023JE007859
04/01/2024
DOI: 10.1029/2023JE007859
Abstract
Juno flew over the northern mid-latitudes of Ganymede during orbit 34 of the Juno mission, reaching an altitude of 1,053 km (16:56:07.972 UTC) at a sub spacecraft latitude/longitude of 33.66N, 57.5W degrees on 7 June 2021. Between 16:43 and 17:02 UT, Juno pierced Ganymede's magnetosphere at a velocity relative to Ganymede of 18.57 km s-1. Juno's instrumentation provided a unique opportunity to sample the local environment of Ganymede and its magnetosphere. We present measurements of the composition of the polar ionospheric outflow and the energetic electrons that penetrate Ganymede's atmosphere and produce its aurora. When these new observations are combined with modeling, conclusions can be drawn that affect our understanding of the atmosphere of Ganymede. The measured JADE precipitating plasma electrons provide an energy flux beyond that needed to create the observed oxygen emissions measured by UVS, but the electron energy spectrum is optically thin to the sparse atmosphere and does not provide the observed oxygen ultraviolet emission unless the O2 column density is increased by over an order of magnitude compared to previous atmospheric models. More than 99% of the electron energy flux passes through the atmosphere into the ice, thereby increasing the H2 and O2 content of the atmosphere. The increased H2 and O2 production is largely responsible for increasing the oxygen column density to a level that produces within known uncertainties the OI135.6 and OI130.4 nm emissions when bombarded by the electron energy flux observed by JADE. This suggests that past modeling efforts have underestimated the density of the atmosphere by over an order of magnitude.
Juno flew by the Jovian satellite Ganymede on orbit 34 of the mission coming within 1,053 km of the surface at high northern latitudes. Juno provides a unique data set from the particle, field, and ultraviolet imaging experiments that can be utilized to study the interaction between the magnetosphere of Ganymede and the magnetosphere of Jupiter. Compositionally diverse ion outflow was observed in the northern polar cap that can be linked to the exchange of plasma and energetic particles between Jupiter and Ganymede. Furthermore, an electron spectrum produced by magnetic reconnection processes was observed that can be linked to the aurora at Ganymede. These observations provide new information about Ganymede's atmosphere. They strongly suggest an increase in the column density of O2 in Ganymede's atmosphere of an order of magnitude relative to all previous models. The latter has implications for all water ice satellites in the outer solar system.
Multiple data sets from Juno's flyby of Ganymede indicate energetic particle impact of the surface and atmosphere resulting in ion outflow Reconnection processes on the Jupiter-facing flank of the magnetospheric interaction provide constraints on the auroral excitation Initial modeling strongly suggests an order of magnitude increase in atmospheric O2 column density relative to previous models
Details
- Title: Subtitle
- Magnetospheric-Ionospheric-Atmospheric Implications From the Juno Flyby of Ganymede
- Creators
- J. H Waite Jr - Waite Sci LLC, Pensacola, FL 32507 USAT. K. Greathouse - Southwest Research InstituteS. R. Carberry Mogan - University of California, BerkeleyA. H. Sulaiman - University of MinnesotaP. Valek - Southwest Research InstituteF. Allegrini - Southwest Research InstituteR. W. Ebert - Southwest Research InstituteG. R. Gladstone - Southwest Research InstituteW. S. Kurth - University of IowaJ. E. P. Connerney - Space Res Corp, Annapolis, MD USAG. Clark - Johns Hopkins University Applied Physics LaboratoryF. Bagenal - University of Colorado BoulderS. Duling - University of CologneN. Romanelli - University of Maryland, College ParkS. Bolton - Southwest Research InstituteA. Vorburger - University of BernC. Paranicas - Johns Hopkins University Applied Physics LaboratoryP. Kollmann - Johns Hopkins University Applied Physics LaboratoryB. Mauk - Johns Hopkins University Applied Physics LaboratoryC. Hansen - Planetary Science InstituteD. Buccino - Jet Propulsion LaboratoryR. E. Johnson - University of VirginiaR. J. Wilson - Laboratory for Atmospheric and Space PhysicsB. Teolis - Southwest Research Institute
- Resource Type
- Journal article
- Publication Details
- Journal of geophysical research. Planets, Vol.129(4), e2023JE007859
- Publisher
- Amer Geophysical Union
- DOI
- 10.1029/2023JE007859
- ISSN
- 2169-9097
- eISSN
- 2169-9100
- Number of pages
- 20
- Grant note
- 884711 / European Research Council (ERC) under the European Union; European Research Council (ERC) 80NSSC23K0276 / NASA NFDAP 80NSSC21K0152; NNX16AR99G / Solar System Workings (SSW) 80NM0018D0004 / National Aeronautics and Space Administration; National Aeronautics & Space Administration (NASA) NASA's New Frontiers Program for Juno NASA; National Aeronautics & Space Administration (NASA) Southwest Research Institute
- Language
- English
- Date published
- 04/01/2024
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984618874202771
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