Evidence of Europa Neutral Gas Torii From Energetic Sulfur Ion Measurements

Nénon, Q.; André, Nicolas

doi:10.1029/2019gl082200

Cited by 24 publications

(48 citation statements)

References 22 publications

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“…Recently, Nénon and André (2019) note the removal of energetic (~MeV) sulfur ions with ~90° pitch angle near Europa's magnetic flux shell. Based on the relative cross sections at these energies and an estimate of the neutral clouds densities (Smith et al, 2019), they argue that inward‐transported energetic sulfur ions interact mainly with the extended hydrogen cloud while protons interact mainly with the tenuous, more equatorially confined oxygen cloud.…”

Section: Neutral Cloudsmentioning

confidence: 99%

“…When protons charge exchange with Europa's neutral hydrogen and oxygen clouds, they are lost as vENAs—as detected by the Cassini MIMI instrument (Krimigis et al, 2002; Mauk et al, 2004). Nénon and André (2019) point out that since the heavy energetic ions tend to be higher ionization states (Clark et al, 2016), their interaction with Europa's neutral clouds reduces their charge state so that when they move inward to Io's neutral cloud they are singly charged (Mauk et al, 2004). After charge exchanging with Io's neutral clouds, the heavy neutrals might leave the system as vENAs although such heavy vENAs have not yet been observed.…”

Section: Neutral Cloudsmentioning

confidence: 99%

“…After charge exchanging with Io's neutral clouds, the heavy neutrals might leave the system as vENAs although such heavy vENAs have not yet been observed. The estimates of the Europa neutral cloud density of Mauk et al (2004) and the conjecture of Nénon and André (2019) on the neutral clouds composition and extent are based on first‐order calculations and ultimately will be tested by the Jovian Energetic Neutral and Ions instrument onboard the ESA JUICE mission to Jupiter.…”

Section: Neutral Cloudsmentioning

confidence: 99%

“…The population of energetic electrons monotonically increases as they move inward through the Io‐Europa region (Jun et al, 2005; Nénon et al, 2017). Note that all ion species in Galileo EPD data show a sharp drop as they move inward past Europa's orbit (Kollmann et al, 2016; Lagg et al, 1998, 2003; Nénon et al, 2018; Nénon & André, 2019). This structure is primarily due to charge exchange reactions of the inward‐moving energetic ions with the neutral clouds of Europa and Io (illustrated in Figure 13 from the modeling of Smith et al, 2019).…”

Section: Plasma Torusmentioning

confidence: 99%

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The Space Environment of Io and Europa

2020

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The Galilean moons play major roles in the giant magnetosphere of Jupiter. At the same time, the magnetospheric particles and fields affect the moons. The impact of magnetospheric ions on the moons' atmospheres supplies clouds of escaping neutral atoms that populate a substantial fraction of their orbits. At the same time, ionization of atoms in the neutral cloud is the primary source of magnetospheric plasma. The stability of this feedback loop depends on the plasma/moon-atmosphere interaction. The purpose of this review is to describe the physical processes that shape the space environment around the two innermost Galilean moons-Io and Europa-and to show their impact from the planet Jupiter out into interplanetary space.

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Section: Neutral Cloudsmentioning

confidence: 99%

Section: Neutral Cloudsmentioning

confidence: 99%

Section: Neutral Cloudsmentioning

confidence: 99%

Section: Plasma Torusmentioning

confidence: 99%

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The Space Environment of Io and Europa

2020

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“…Clark et al (2016) showed that charge states are not uniform but have a distribution. Nénon and André (2019) demonstrated that energetic ion charge states likely evolve with energy and distance from Jupiter. Selesnick and Cohen (2009) suggest that at the highest energies, heavy ions may be fully ionized.…”

Section: Particle Tracing Model Gentoomentioning

confidence: 99%

Energetic Ion Dynamics in the Perturbed Electromagnetic Fields Near Europa

et al. 2019

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We model the dynamics of energetic magnetospheric ions in the perturbed electromagnetic fields near Jupiter's moon Europa. The inhomogeneities in the fields near Europa are generated by the induced dipole field from the moon's subsurface ocean as well as the Alfvénic plasma interaction with its ionosphere and induced field. Inhomogeneities in Europa's ionosphere at various length scales generate substantial asymmetries in the mass loading process that further complicate the structure of the moon's electromagnetic environment. In our study, the electromagnetic fields near Europa are obtained from an established hybrid model, whereas a particle tracing tool is applied to analyze the precipitation of the three most abundant energetic ion species (hydrogen, oxygen, and sulfur) onto the moon's surface at various energies from 1 keV up to 5 MeV. To isolate the contributions of the induced dipole and ionospheric mass loading to the field perturbations and the resulting precipitation patterns, we consider multiple field configurations of successively increasing complexity. For ion energies in the kiloelectron volt regime, magnetic field line draping effectively shields large portions of Europa's surface against energetic ion impacts and drastically alters the shape of the precipitation patterns, compared to uniform fields. The fine structure of these patterns strongly depends on the complexity of the applied ionosphere model. Only in the megaelectron volt regime, the precipitation patterns are qualitatively similar for uniform and draped fields. However, the precipitation of megaelectron volt ions onto Europa is still not homogeneous, since the strong magnetospheric field keeps ion gyroradii much smaller than the moon's radius.

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