Water‐Group Pickup Ions From Europa‐Genic Neutrals Orbiting Jupiter

Szalay, J. R.; Smith, H. T.; Zirnstein, E. J.; McComas, D. J.; Begley, L. J.; Bagenal, F.; Delamere, P. A.; Wilson, R.; Valek, P. W.; Poppe, A. R.; Nénon, Q.; Allegrini, F.; Ebert, R. W.; Bolton, S. J.

doi:10.1029/2022gl098111

Cited by 28 publications

(37 citation statements)

References 49 publications

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“…The simulated H 2 neutral loss rates from Callisto presented here (Section 4.2) are larger than those derived for Europa by Szalay et al. (2022). Moreover, since the neutral lifetimes are much shorter at Europa (Oza et al., 2019), its toroidal cloud's spatial extent is more confined than at Callisto.…”

Section: Discussion and Constraintscontrasting

confidence: 67%

“…Although results from their analysis were consistent with those of Lagg et al (2003), since the source rate of energetic particles near Europa's orbit is not well known, they could only make a relatively broad constraint for equatorial H 2 of ∼1-410 cm −3 . From recent Juno observations, Szalay et al (2022) confirmed the presence of a Europa-genic neutral H 2 toroidal cloud, which is expected to be the primary cloud constituent (Smith et al, 2019). However, since they were derived from 𝐴𝐴 H + 2 pickup ion densities, they refrained from estimating the concomitant neutral H 2 densities in the toroidal cloud, and suggested more complex modeling is required to do so.…”

Section: Tablementioning

confidence: 99%

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Callisto's Atmosphere: First Evidence for H₂ and Constraints on H₂O

et al. 2022

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As the most geologically primitive of the icy Galilean satellites, Callisto has the least well understood atmosphere, limiting our understanding of the evolution of the objects in this important system, soon to be the subject of multiple new spacecraft observations. There is no consensus on the state of water ice on its surface nor how that correlates with the production of atmospheric water vapor. Similarly, although radiolysis is likely the primary source of O 2 in Callisto's atmosphere (Cunningham et al., 2015), the concomitant H 2 component has not yet been identified. Forthcoming exploration of Callisto by ESA's JUpiter ICy moons Explorer (JUICE; e.g., Galli et al., 2022), NASA's Europa Clipper, and CNSA's planned Gan De can help resolve such issues. With

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Section: Discussion and Constraintscontrasting

confidence: 67%

Section: Tablementioning

confidence: 99%

Callisto's Atmosphere: First Evidence for H₂ and Constraints on H₂O

et al. 2022

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“…Panel (b) shows typical ion composition in Jupiter's plasma disk (T. K. H. Kim et al., 2020). The presence and abundance of H 2 + is consistent with a population of radially transported pickup ions from Europa's neutral H 2 toroidal cloud (Szalay et al., 2022).…”

Section: Ion Compositionsupporting

confidence: 59%

Plasma Observations During the 7 June 2021 Ganymede Flyby From the Jovian Auroral Distributions Experiment (JADE) on Juno

Allegrini

Bagenal

Ebert

et al. 2022

Geophysical Research Letters

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Most of what is known from the interaction of Ganymede with Jupiter's magnetosphere originates from six Galileo close flybys (ranging from 264.4 to 3,104.9 km in altitude) (e.g., Kivelson et al., 2022).Approaching its 34th perijove, Juno came as close as 1,046 km from Ganymede's surface (sub-spacecraft latitude of 23.6°N) on 7 June 2021 (Hansen et al., 2022). Juno approached Ganymede from southern latitudes, passed through a part of the wake region that was unexplored by previous missions, through its magnetosphere to closest approach on the night side, then to the dayside, and went back into the plasma disk toward Jupiter. Highlights of the flyby from Juno's suite of instruments are reported in this issue.In this paper, we summarize plasma observations made by the Jovian Auroral Distributions Experiment (McComas et al., 2017). JADE consists of two electron (JADE-E) and one ion (JADE-I) sensors. JADE-E are top-hat analyzers measuring 0.032-32 keV electron distributions at 1 s time resolution. JADE-I has a top-hat analyzer and a time-of-flight (TOF) section to determine ion energy-per-charge (E/q) and mass-per-charge (m/q)

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“…Marconi (2007) estimates escape rates of 3.0 × 10 26 H/s and of 1.3 × 10 27 H 2 /s, which might yet be higher if both H and H 2 atmospheres from Marconi (2007) indeed need to be up-scaled in density to agree with the observational constraints on the H corona (see discussion in previous paragraph). On the other hand, observations of H + 2 pick-up ions by the Juno spacecraft did not reveal a substantial source of the ions at Ganymede's orbit limiting the H 2 neutral density and thus loss rate to 2.0×10 26 H 2 /s (50% of Europa's rate) or lower (Szalay et al 2022). Taken together, the H corona density suggests H 2 loss rates from the atmosphere (via simulations) that are more than one order of magnitude higher than the constraints from H + 2 pick-up ions, suggesting that the pathways of gaseous neutral hydrogen species from the icy moons are not fully understood yet.…”

Section: Discussionmentioning

confidence: 89%

Probing Ganymede's atmosphere with HST Ly$α$ images in transit of Jupiter

Roth¹,

Gregorio²,

Becker³

et al. 2023

Preprint

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We report results from far-ultraviolet observations by the Hubble Space Telescope of Jupiter's largest moon Ganymede transiting across the planet's dayside hemisphere. Within a targeted campaign on 9 September 2021 two exposures were taken during one transit passage to probe for attenuation of Jupiter's hydrogen Lyman-α dayglow above the moon limb. The background dayglow is slightly attenuated over an extended region around Ganymede, with stronger attenuation in the second exposure when Ganymede was near the planet's center. In the first exposure when the moon was closer to Jupiter's limb, the effects from the Ganymede corona are hardly detectable, likely because the Jovian Lyman-α dayglow is spectrally broader and less intense at this viewing geometry. The obtained vertical H column densities of around (1 − 2) × 10 12 cm −2 are consistent with previous results. Constraining angular variability around Ganymede's disk, we derive an upper limit on a local H 2 O column density of (2 − 3) × 10 16 cm −2 , such as could arise from outgassing plumes in regions near the observed moon limb.

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Water‐Group Pickup Ions From Europa‐Genic Neutrals Orbiting Jupiter

Cited by 28 publications

References 49 publications

Callisto's Atmosphere: First Evidence for H₂ and Constraints on H₂O

Callisto's Atmosphere: First Evidence for H₂ and Constraints on H₂O

Plasma Observations During the 7 June 2021 Ganymede Flyby From the Jovian Auroral Distributions Experiment (JADE) on Juno

Probing Ganymede's atmosphere with HST Ly$α$ images in transit of Jupiter

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Water‐Group Pickup Ions From Europa‐Genic Neutrals Orbiting Jupiter

Cited by 28 publications

References 49 publications

Callisto's Atmosphere: First Evidence for H2 and Constraints on H2O

Callisto's Atmosphere: First Evidence for H2 and Constraints on H2O

Plasma Observations During the 7 June 2021 Ganymede Flyby From the Jovian Auroral Distributions Experiment (JADE) on Juno

Probing Ganymede's atmosphere with HST Ly$α$ images in transit of Jupiter

Contact Info

Product

Resources

About

Callisto's Atmosphere: First Evidence for H₂ and Constraints on H₂O

Callisto's Atmosphere: First Evidence for H₂ and Constraints on H₂O