Exospheres and Atmospheric Escape

Johnson, R. E.; Combi, M. R.; Fox, Jane L.; Ip, Wing-Huen; Leblanc, François; McGrath, M. A.; Shematovich, V. I.; Strobel, D. F.; Waite, J. H.

doi:10.1007/s11214-008-9415-3

Cited by 111 publications

(105 citation statements)

References 293 publications

(333 reference statements)

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“…Very little information is available on momentum transfer cross-sections, which depend on the composition of the ions and neutrals, as well as the energy of the ions and electrons (Johnson et al 2008). The electronneutral momentum transfer cross-section has been estimated for 5 eV electrons to be ∼5 × 10 −16 cm 2 (Itikawa & Mason 2005), while the ion-neutral cross-section is estimated to be between 2 × 10 −15 cm 2 for solar wind ions and 8 × 10 −15 cm 2 for mass loaded solar wind with a bulk composition of H 2 O + (Mendis et al 1986).…”

Section: The Collisionopausementioning

confidence: 99%

RPC observation of the development and evolution of plasma interaction boundaries at 67P/Churyumov-Gerasimenko

Mandt

Eriksson

Edberg

et al. 2016

Mon. Not. R. Astron. Soc.

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One of the primary objectives of the Rosetta Plasma Consortium, a suite of five plasma instruments on-board the Rosetta spacecraft, is to observe the formation and evolution of plasma interaction regions at the comet 67P/Churyumov-Gerasimenko (67P/CG). Observations made between 2015 April and 2016 February show that solar wind-cometary plasma interaction boundaries and regions formed around 2015 mid-April and lasted through early 2016 January. At least two regions were observed, separated by an ion-neutral collisionopause boundary. The inner region was located on the nucleus side of the boundary and was characterized by low-energy water-group ions, reduced magnetic field pileup and enhanced electron densities. The outer region was located outside of the boundary and was characterized by reduced electron densities, water-group ions that are accelerated to energies above 100 eV and enhanced magnetic field pileup compared to the inner region. The boundary discussed here is outside of the diamagnetic cavity and shows characteristics similar to observations made on-board the Giotto spacecraft in the ion pileup region at 1P/Halley. We find that the boundary is likely to be related to ion-neutral collisions and that its location is influenced by variability in the neutral density and the solar wind dynamic pressure.

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Section: The Collisionopausementioning

confidence: 99%

RPC observation of the development and evolution of plasma interaction boundaries at 67P/Churyumov-Gerasimenko

Mandt

Eriksson

Edberg

et al. 2016

Mon. Not. R. Astron. Soc.

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“…Therefore, understanding Mars' exosphere helps us understand Martian atmospheric escape and its effect on Martian climatic change (Chassefière et al 2007). This section can be considered as a complement of the recent review about escape modeling done by Johnson et al (2008), which focuses on the Martian neutral exosphere.…”

Section: The Neutral Exosphere Of Marsmentioning

confidence: 99%

“…The hot oxygen atoms formed by dissociative recombination of O + 2 can produce a recoil population through a cascade of collisions with the thermal oxygen population (Shematovich et al 1994). Other sources of hot neutral oxygen such as sputtering, due to the precipitation of accelerated pick-up O + ions into the Martian atmosphere, are less important in current conditions (Chaufray et al 2007) but could have played a more important role in the past (Leblanc and Johnson 2001;Johnson et al 2008). Moreover, recent detections of energetic neutral atoms (ENAs) produced by charge exchange between energetic ions and the neutral exosphere require accurate coupling between the neutral exosphere and solar wind (Futaana et al 2011).…”

Section: The Neutral Exosphere Of Marsmentioning

confidence: 99%

Modeling of Venus, Mars, and Titan

Kallio

Chaufray

Modolo

et al. 2011

Space Sciences Series of ISSI

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Increased computer capacity has made it possible to model the global plasma and neutral dynamics near Venus, Mars and Saturn's moon Titan. The plasma interactions at Venus, Mars, and Titan are similar because each possess a substantial atmosphere but lacks a global internally generated magnetic field. In this article three self-consistent plasma models are described: the magnetohydrodynamic (MHD) model, the hybrid model and the fully kinetic plasma model. are also described. In particular, we describe the pros and cons of each model approach. Results from simulations are presented to demonstrate the ability of the models to capture the known plasma and neutral dynamics near the three objects.

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“…A number of nonthermal mechanisms were investigated in previous works (Johnson et al 2008, and references therein). The DSMC modeling of Shematovich et al (2003) predicted a total nitrogen escape rate of3.6 10 25 s −1 in the form of N 2 and N, due to sputtering by incident magnetospheric ions and pick-up ions.…”

Section: Discussion and Concluding Remarksmentioning

confidence: 99%

“…Such a suprathermal population was thought to be contributed by momentum transfer from solar wind (SW) energetic protons to atomic H in the Venusian upper atmosphere (Hodges 1999). A hot O corona on Venus was also revealed by 130.4nm observations made with the UV spectrometer on board Pioneer Venus Orbiter (PVO) (Nagy et al 1981) and Venera 11 and 12 (Bertaux et al 1981), and was thought to be produced by dissociative recombination of + O 2 , the dominant constituent of the Venusian ionosphere (Johnson et al 2008). However, the presence of this hot O corona was not confirmed by more recent VEx SPICAV observations (Lichtenegger et al 2009).…”

Section: Introductionmentioning

confidence: 99%

The Structure of Titan’s N₂ and CH₄ Coronae

Jiang

Cui

2017

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In this study, we analyze the structures of Titan's N 2 and CH 4 coronae using a large data set acquired by the Ion Neutral Mass Spectrometer (INMS) instrument on board Cassini. The N 2 and CH 4 densities measured from the exobase up to 2000km imply a mean exobase temperature of 146K and 143K, respectively, which is lower than the mean upper atmospheric temperature by 4 and 7K. This indicates that on average, Titan possesses a subthermal rather than suprathermal corona. A careful examination reveals that the variability in corona structure is not very likely to be solar driven. Within the framework of the collisionless kinetic model, we investigate how the CH 4 energy distribution near the exobase could be constrained if strong CH 4 escape occurs on Titan. Several functional forms for the CH 4 energy distribution are attempted, assuming two representative CH 4 escape rates of 1.2 10 25 s −1 and2.2 10 27 s −1. We find that the double Maxwellian and power-law distributions can reproduce the shape of the CH 4 corona structure as well as the imposed CH 4 escape rate. In both cases, the escape rate is contributed by a suprathermal CH 4 population on the high-energy tail, with a number fraction below 5% and a characteristic energy of 0.1-0.6eV per suprathermal CH 4 molecule. The coexistence of the subthermal CH 4 corona revealed by the INMS data and substantial CH 4 escape suggested by some previous works could be reconciled by a significant departure in the exobase CH 4 energy distribution from ideal Maxwellian that enhances escape and causes a noticeable redistribution of the corona structure.

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Exospheres and Atmospheric Escape

Abstract: International audienceAeronomy is a description of the physics and chemistry of the upper atmospheres and ionospheres of planetary bodies. In this chapter we consider those processes occurring in the upper atmosphere that determine the structure of the corona and lead to molecular escape

Cited by 111 publications

References 293 publications

RPC observation of the development and evolution of plasma interaction boundaries at 67P/Churyumov-Gerasimenko

RPC observation of the development and evolution of plasma interaction boundaries at 67P/Churyumov-Gerasimenko

Modeling of Venus, Mars, and Titan

The Structure of Titan’s N₂ and CH₄ Coronae

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Exospheres and Atmospheric Escape

Abstract: International audienceAeronomy is a description of the physics and chemistry of the upper atmospheres and ionospheres of planetary bodies. In this chapter we consider those processes occurring in the upper atmosphere that determine the structure of the corona and lead to molecular escape

Cited by 111 publications

References 293 publications

RPC observation of the development and evolution of plasma interaction boundaries at 67P/Churyumov-Gerasimenko

RPC observation of the development and evolution of plasma interaction boundaries at 67P/Churyumov-Gerasimenko

Modeling of Venus, Mars, and Titan

The Structure of Titan’s N2 and CH4 Coronae

Contact Info

Product

Resources

About

The Structure of Titan’s N₂ and CH₄ Coronae