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Magnetospheric‐Ionospheric‐Atmospheric Implications From the Juno Flyby of Ganymede.

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Title: Magnetospheric‐Ionospheric‐Atmospheric Implications From the Juno Flyby of Ganymede.
Authors: Waite, J. H.1 (AUTHOR) hunterwaite@gmail.com, Greathouse, T. K.2 (AUTHOR), Carberry Mogan, S. R.3 (AUTHOR), Sulaiman, A. H.4 (AUTHOR), Valek, P.2 (AUTHOR), Allegrini, F.2 (AUTHOR), Ebert, R. W.2 (AUTHOR), Gladstone, G. R.2 (AUTHOR), Kurth, W. S.5 (AUTHOR), Connerney, J. E. P.6 (AUTHOR), Clark, G.7 (AUTHOR), Bagenal, F.8 (AUTHOR), Duling, S.9 (AUTHOR), Romanelli, N.10,11 (AUTHOR), Bolton, S.2 (AUTHOR), Vorburger, A.12 (AUTHOR), Paranicas, C.7 (AUTHOR), Kollmann, P.7 (AUTHOR), Mauk, B.7 (AUTHOR), Hansen, C.13 (AUTHOR)
Source: Journal of Geophysical Research. Planets. Apr2024, Vol. 129 Issue 4, p1-20. 20p.
Subject Terms: *Atmosphere, Atmospheric oxygen, Natural satellites, Magnetic reconnection, Atmospheric models, Specific gravity, Relative velocity, Latitude
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. Plain Language Summary: 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. Key Points: Multiple data sets from Juno's flyby of Ganymede indicate energetic particle impact of the surface and atmosphere resulting in ion outflowReconnection processes on the Jupiter‐facing flank of the magnetospheric interaction provide constraints on the auroral excitationInitial modeling strongly suggests an order of magnitude increase in atmospheric O2 column density relative to previous models [ABSTRACT FROM AUTHOR]
Copyright of Journal of Geophysical Research. Planets is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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  Data: Magnetospheric‐Ionospheric‐Atmospheric Implications From the Juno Flyby of Ganymede.
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  Data: <searchLink fieldCode="AR" term="%22Waite%2C+J%2E+H%2E%22">Waite, J. H.</searchLink><relatesTo>1</relatesTo> (AUTHOR)<i> hunterwaite@gmail.com</i><br /><searchLink fieldCode="AR" term="%22Greathouse%2C+T%2E+K%2E%22">Greathouse, T. K.</searchLink><relatesTo>2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Carberry+Mogan%2C+S%2E+R%2E%22">Carberry Mogan, S. R.</searchLink><relatesTo>3</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Sulaiman%2C+A%2E+H%2E%22">Sulaiman, A. H.</searchLink><relatesTo>4</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Valek%2C+P%2E%22">Valek, P.</searchLink><relatesTo>2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Allegrini%2C+F%2E%22">Allegrini, F.</searchLink><relatesTo>2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Ebert%2C+R%2E+W%2E%22">Ebert, R. W.</searchLink><relatesTo>2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Gladstone%2C+G%2E+R%2E%22">Gladstone, G. R.</searchLink><relatesTo>2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Kurth%2C+W%2E+S%2E%22">Kurth, W. S.</searchLink><relatesTo>5</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Connerney%2C+J%2E+E%2E+P%2E%22">Connerney, J. E. P.</searchLink><relatesTo>6</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Clark%2C+G%2E%22">Clark, G.</searchLink><relatesTo>7</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Bagenal%2C+F%2E%22">Bagenal, F.</searchLink><relatesTo>8</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Duling%2C+S%2E%22">Duling, S.</searchLink><relatesTo>9</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Romanelli%2C+N%2E%22">Romanelli, N.</searchLink><relatesTo>10,11</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Bolton%2C+S%2E%22">Bolton, S.</searchLink><relatesTo>2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Vorburger%2C+A%2E%22">Vorburger, A.</searchLink><relatesTo>12</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Paranicas%2C+C%2E%22">Paranicas, C.</searchLink><relatesTo>7</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Kollmann%2C+P%2E%22">Kollmann, P.</searchLink><relatesTo>7</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Mauk%2C+B%2E%22">Mauk, B.</searchLink><relatesTo>7</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Hansen%2C+C%2E%22">Hansen, C.</searchLink><relatesTo>13</relatesTo> (AUTHOR)
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  Data: <searchLink fieldCode="JN" term="%22Journal+of+Geophysical+Research%2E+Planets%22">Journal of Geophysical Research. Planets</searchLink>. Apr2024, Vol. 129 Issue 4, p1-20. 20p.
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  Data: 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. Plain Language Summary: 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. Key Points: Multiple data sets from Juno's flyby of Ganymede indicate energetic particle impact of the surface and atmosphere resulting in ion outflowReconnection processes on the Jupiter‐facing flank of the magnetospheric interaction provide constraints on the auroral excitationInitial modeling strongly suggests an order of magnitude increase in atmospheric O2 column density relative to previous models [ABSTRACT FROM AUTHOR]
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  Data: <i>Copyright of Journal of Geophysical Research. Planets is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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