In Situ Ion Composition Observations of Ganymede's Outflowing Ionosphere

P. W. Valek; J. H. Waite; F. Allegrini; R. W. Ebert; F. Bagenal; S. J. Bolton; J. E. P. Connerney; W. S. Kurth; J. R. Szalay; R. J. Wilson

doi:10.1029/2022GL100281

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In Situ Ion Composition Observations of Ganymede's Outflowing Ionosphere

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In Situ Ion Composition Observations of Ganymede's Outflowing Ionosphere

P. W. Valek, J. H. Waite, F. Allegrini, R. W. Ebert, F. Bagenal, S. J. Bolton, J. E. P. Connerney, W. S. Kurth, J. R. Szalay and R. J. Wilson

Geophysical research letters, Vol.49(24), e2022GL100281

12/28/2022

DOI: 10.1029/2022GL100281

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Abstract

On 7 June 2021 the Juno spacecraft passed through the Ganymede magnetosphere, with a closest approach altitude of 1,046 km. The Jovian Auroral Distributions Experiment‐Ion (JADE‐I) sensor observed ionospheric ions, consisting of O2+, O+, H2+, H+, and H3+. These ions were outflowing, with no bi‐directional flow except possibly near the magnetopause. Relative ion densities with respect to time agree the electron density determined by the Waves instrument, but are ∼2.5 times larger. The light ions appear to be in hydrostatic equilibrium because the altitude profile is generally symmetric between inbound and outbound legs of the flyby. H3+ ions are an exception to this, with the ratio of H3+/H2+ being ∼a factor 4 lower on the outbound than the inbound leg. The heavy ions have higher densities outbound than inbound. The outflowing flux of light ions peak near closest approach, but the heavy ions peak outbound of the flyby. Plain Language Summary On 7 June 2021 the Juno spacecraft passed through the Ganymede magnetosphere, with a closest approach altitude of 1,046 km. During this flyby, the Jovian Auroral Distributions Experiment‐Ion (JADE‐I) sensor observed ions flowing out from the ionosphere. The JADE‐I observations are the first direct measurement of the composition of the ionospheric ions. This is an important measurement since there is currently not consensus of the composition. These ionospheric ions consist of O2+, O+, H2+, H+, and H3+. The different species have different altitude profiles. The light ions altitude profile is generally symmetric between inbound and outbound legs of the flyby. H3+ ions are an exception to this, with the ratio of H3+/H2+ being ∼a factor 4 lower on the outbound than the inbound leg. The heavy ions have higher densities outbound than inbound. Key Points First in situ, ion composition observations of Ganymede’s outflowing ionosphere Low energy ions consist of O2+, O+, H2+, H+, and H3+ Light ions and heavy have different altitude profiles and spatial profiles

Ionosphere

Ganymede

ion composition

JADE

Juno

Details

Title: Subtitle: In Situ Ion Composition Observations of Ganymede's Outflowing Ionosphere
Creators: P. W. Valek - Southwest Research Institute
J. H. Waite - Southwest Research Institute
F. Allegrini - Southwest Research Institute
R. W. Ebert - Southwest Research Institute
F. Bagenal - Laboratory for Atmospheric and Space Physics
S. J. Bolton - Southwest Research Institute
J. E. P. Connerney - Goddard Space Flight Center
W. S. Kurth - University of Iowa
J. R. Szalay - Princeton University
R. J. Wilson - Laboratory for Atmospheric and Space Physics
Resource Type: Journal article
Publication Details: Geophysical research letters, Vol.49(24), e2022GL100281
DOI: 10.1029/2022GL100281
ISSN: 0094-8276
eISSN: 1944-8007
Number of pages: 7
Grant note: NASA New Frontiers Program for Juno (NNM06AA75C) NASA's Juno mission
Language: English
Date published: 12/28/2022
Academic Unit: Physics and Astronomy
Record Identifier: 9984455660202771

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