First ENA observations at Mars: ENA emissions from the martian upper atmosphere

Futaana, Yoshifumi; Barabash, S.; Grigoriev, Alexander; Holmström, Mats; Kallio, Esa; Brandt, P. C.; Gunell, H.; Brinkfeldt, K.; Lundin, R.; Andersson, H.; Yamauchi, M.; McKenna-Lawler, S.; Winningham, J. D.; Frahm, R. A.; Sharber, J. R.; Scherrer, J.; Coates, A. J.; Linder, Dietmar; Kataria, D. O.; Säles, T.; Riihelä, P.; Schmidt, W.; Koskinen, Hannu E. J.; Kozyra, J. U.; Luhmann, J. G.; Roelof, E. C.; Williams, D. J.; Livi, S.; Curtis, C. C.; Hsieh, K. C.; Sandel, B. R.; Grandé, M.; Carter, M.; Sauvaud, J. A.; Fedorov, A.; Thocaven, J. J.; Orsini, S.; Cerulli-Irelli, R.; Maggi, M.; Würz, Peter; Bochsler, P.; Galli, André; Krupp, N.; Woch, J.; Fränz, M.; Asamura, Kazushi; Dierker, C.

doi:10.1016/j.icarus.2005.09.019

Cited by 61 publications

(56 citation statements)

References 15 publications

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“…(A color version of this figure is available in the online journal.) low probable, large-angle collisions: for example, determination of the back scattering intensity (albedo) of helium ENA fluxes from planetary atmospheres (Futaana et al 2006) or investigations of high momentum-transfer collisions in the escape process (Bovino et al 2011). Large-angle (small impact parameter) scattering of atomic particles at high collision energies requires consideration of inelastic scattering channels even for cases when the total elastic cross section is significantly larger than inelastic ones, which is out of the scope of the present investigation and plays a minor role in the energy relaxation of fast helium atoms.…”

Section: Differential Cross Sectionsmentioning

confidence: 99%

“…Some possible mechanisms for the creation of keV energetic neutral atoms (ENAs) in the heliosphere include the charge exchange collision of solar wind alpha particles with thermal neutral atoms from the interstellar gas (McComas et al 2011;Hilchenbach et al 1998;Gruntman 1997). Another important example involves charge exchange collisions between keV solar wind ions and neutral atoms and molecules from planetary and cometary atmospheres (Krasnopolsky & Gladstone 2005), a process which has been seen on Mars and Venus (Galli et al 2006(Galli et al , 2008Futaana et al 2006;Luhmann et al 1992). For magnetized planets, interaction of the magnetospheric ions with planetary or satellite atmospheres can be considered as a regular source of energetic atoms (Lui et al 1996).…”

Section: Introductionmentioning

confidence: 99%

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Energy Relaxation of Helium Atoms in Astrophysical Gases

Lewkow

Kharchenko

Zhang

2012

ApJ

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We report accurate parameters describing energy relaxation of He atoms in atomic gases, important for astrophysics and atmospheric science. Collisional energy exchange between helium atoms and atomic constituents of the interstellar gas, heliosphere, and upper planetary atmosphere has been investigated. Energy transfer rates, number of collisions required for thermalization, energy distributions of recoil atoms, and other major parameters of energy relaxation for fast He atoms in thermal H, He, and O gases have been computed in a broad interval of energies from 10 meV to 10 keV. This energy interval is important for astrophysical applications involving the energy deposition of energetic atoms and ions into atmospheres of planets and exoplanets, atmospheric evolution, and analysis of non-equilibrium processes in the interstellar gas and heliosphere. Angular-and energy-dependent cross sections, required for an accurate description of the momentum-energy transfer, are obtained using ab initio interaction potentials and quantum mechanical calculations for scattering processes. Calculation methods used include partial wave analysis for collisional energies below 2 keV and the eikonal approximation at energies higher than 100 eV, keeping a significant energy region of overlap, 0.1-2 keV, between these two methods for their mutual verification. The partial wave method and the eikonal approximation excellently match results obtained with each other as well as experimental data, providing reliable cross sections in the astrophysically important interval of energies from 10 meV to 10 keV. Analytical formulae, interpolating obtained energy-and angular-dependent cross sections, are presented to simplify potential applications of the reported database. Thermalization of fast He atoms in the interstellar gas and energy relaxation of hot He and O atoms in the upper atmosphere of Mars are considered as illustrative examples of potential applications of the new database.

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Section: Differential Cross Sectionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Energy Relaxation of Helium Atoms in Astrophysical Gases

Lewkow

Kharchenko

Zhang

2012

ApJ

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“…The dayside magnetosheath and magnetosphere are a source of charge exchange and backscattered ENAs [Futaana et al, 2006a;Gunell et al, 2006a;Futaana et al, 2006c]. Figure 2a shows a TOF time spectrum of the ENAs observed by NPD1 Dir1 during the nominal case.…”

Section: Nominal Case: No Anomalymentioning

confidence: 99%

Influence of Martian crustal magnetic anomalies on the emission of energetic neutral hydrogen atoms

et al. 2014

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We analyze the data on hydrogen energetic neutral atoms (ENAs) emissions from the dayside of Mars, recorded by a Neutral Particle Detector of the Analyzer of Space Plasmas and Energetic Atoms aboard Mars Express from 14 March to 9 July 2004. We first identify and analyze events of the ENA flux enhancement coinciding with the presence of the crustal magnetic anomalies on the dayside of Mars. We then backtrace the ENA emissions to the lower altitudes (source region) and build up an average map of the flux intensities in the geographic coordinates with all the available data. The map shows a peak-to-valley ENA flux enhancement of 40%-90% close to the crustal magnetic anomaly regions. These results suggest the influence of the magnetic anomalies on the ENA emission from the dayside of Mars. The enhancement may result from the deviation of the highly directional plasma flow above anomalies toward the detectors such that more charge exchange ENAs would be recorded. Alternatively, higher exospheric densities above the anomalies would also result in an increase of the charge exchange ENA flux.

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“…This interaction is characterized by several processes such as charge exchange between plasma protons and the neutral exosphere, leading to energetic neutral atoms (ENA) observed recently by the ASPERA-3 and ASPERA-4 instruments on board Mars Express and Venus Express at Mars (Futaana et al 2006a) and Venus (Galli et al 2008a) respectively and by the MIMI experiment on board Cassini at Titan ). These charge exchange reactions are also an additional source of ionization of the exosphere.…”

Section: Exospherementioning

confidence: 99%

Exospheres and Energetic Neutral Atoms of Mars, Venus and Titan

et al. 2011

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International audienceOur understanding of the upper atmosphere of unmagnetized bodies such as Mars, Venus and Titan has improved significantly in this decade. Recent observations by in situ and remote sensing instruments on board Mars Express, Venus Express and Cassini have revealed characteristics of the neutral upper atmospheres (exospheres) and of energetic neutral atoms (ENAs). The ENA environment in the vicinity of the bodies is by itself a significant study field, but ENAs are also used as a diagnostic tool for the exosphere and the interaction with the upstream plasmas. Synergy between theoretical and modeling work has also improved considerably. In this review, we summarize the recent progress of our understanding of the neutral environment in the vicinity of unmagnetized planets

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First ENA observations at Mars: ENA emissions from the martian upper atmosphere

Cited by 61 publications

References 15 publications

Energy Relaxation of Helium Atoms in Astrophysical Gases

Energy Relaxation of Helium Atoms in Astrophysical Gases

Influence of Martian crustal magnetic anomalies on the emission of energetic neutral hydrogen atoms

Exospheres and Energetic Neutral Atoms of Mars, Venus and Titan

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