Planetary ENA imaging: Effects of different interaction models for Mars

Gunell, H.; Holmström, M.; Barabash, S.; Kallio, Esa; Janhunen, P.; Nagy, A. F.; Ma, Y.

doi:10.1016/j.pss.2005.04.002

Cited by 19 publications

(34 citation statements)

References 13 publications

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“…As comparison to the measurements shown in Figure 9d, Figure 10 shows the predictions for solar wind ENAs of a model from Gunell et al (2006), and Figure 11 shows the predictions for planetary ENAs of the model from Lichtenegger et al (2002), which has to be compared to Figure 9a. The ENA image shown in Figure 10 has been calculated for the observation configuration of the ENA measurements shown in Figure 9d.…”

Section: Flux Statisticsmentioning

confidence: 99%

“…The ENA image shown in Figure 10 has been calculated for the observation configuration of the ENA measurements shown in Figure 9d. In the published version (Gunell et al, 2006) Figure 10. Model of solar wind ENA intensities (Gunell et al, 2006) that has been adapted to the NPD measurement conditions in Figure 9d.…”

Section: Flux Statisticsmentioning

confidence: 99%

“…Lichtenegger et al (2002) The temperature and density of the neutral atomic hydrogen in the exosphere, the strength of the solar wind, and the location of the bow shock and of the induced magnetosphere boundary (see Figure 2), are the most important parameters for the empirical model of Kallio et al (1997) of the solar wind-Mars interaction. This model in general provides a similar global flux distribution as the only parameterized model available (Gunell et al, 2006). 3.…”

Section: Introductionmentioning

confidence: 98%

“…The emission of energetic neutral atoms (ENAs) from Mars has been addressed by several models (Kallio et al, 1997;Holmström et al, 2002;Lichtenegger et al, 2002;Gunell et al, 2006), but direct ENA measurements have become available only since the orbit insertion of ESA's Mars Express (MEX) spacecraft in December 2003. ENA images can give us a global picture of the interaction processes between the solar wind and the Mars atmosphere.…”

Section: Introductionmentioning

confidence: 99%

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Energetic Hydrogen and Oxygen Atoms Observed on the Nightside of Mars

Galli¹,

Würz²,

Barabash

et al. 2006

Space Sci Rev

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We present measurements of energetic hydrogen and oxygen atoms (ENAs) on the nightside of Mars detected by the neutral particle detector (NPD) of ASPERA-3 on Mars Express. We focus on the observations for which the field-of-view of NPD was directed at the nightside of Mars or at the region around the limb, thus monitoring the flow of ENAs towards the nightside of the planet. We derive energy spectra and total fluxes, and have compiled maps of hydrogen ENA outflow. The hydrogen ENA intensities reach 10 5 cm −2 sr −1 s −1 , but no oxygen ENA signals above the detection threshold of 10 4 cm −2 sr −1 s −1 are observed. These intensities are considerably lower than most theoretical predictions. We explain the discrepancy as due to an overestimation of the charge-exchange processes in the models for which too high an exospheric density was assumed. Recent UV limb emission measurements (Galli et al., this issue) point to a hydrogen exobase density of 10 10 m −3 and a very hot hydrogen component, whereas the models were based on a hydrogen exobase density of 10 12 m −3 and a temperature of 200 K predicted by Krasnopolsky and Gladstone (1996). Finally, we estimate the global atmospheric loss rate of hydrogen and oxygen due to the production of ENAs.

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Section: Flux Statisticsmentioning

confidence: 99%

Section: Flux Statisticsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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Energetic Hydrogen and Oxygen Atoms Observed on the Nightside of Mars

Galli¹,

Würz²,

Barabash

et al. 2006

Space Sci Rev

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“…Fortunately, previous observations and simulations showed that the majority of dayside ENAs are emitted near the dayside IMB (∼0.2 R M altitude) [Kallio et al, 1997;Gunell et al, 2006a;Futaana et al, 2006b] where the neutral density is the highest (lowest altitude) and the proton flux is still significant (protons do not penetrate the IMB). Some simulations showed that the most intense source region locates between the bow shock and the IMB, from the subsolar point to a SZA of ∼ 75 • [Kallio et al, 1997;Mura et al, 2002;Holmström and Kallio, 2004;Gunell et al, 2006b]. With this knowledge, we define the source position of the ENAs as (1) the intersection (P1) of its corresponding LOS (LOS1) and the IMB, if they intersect, or (2) the point of the closest approach (P2) of the LOS (LOS2) to the center of Mars, if the LOS and the IMB do not intersect ( Figure 5).…”

Section: Statistical Resultsmentioning

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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Emission of hydrogen energetic neutral atoms from the Martian subsolar magnetosheath

et al. 2016

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We have simulated the hydrogen energetic neutral atom (ENA) emissions from the subsolar magnetosheath of Mars using a hybrid model of the proton plasma charge exchanging with the Martian exosphere to study statistical features revealed from the observations of the Neutral Particle Detectors on Mars Express. The simulations reproduce well the observed enhancement of the hydrogen ENA emissions from the dayside magnetosheath in directions perpendicular to the Sun‐Mars line. Our results show that the neutralized protons from the shocked solar wind are the dominant ENA population rather than those originating from the pickup planetary ions. The simulation also suggests that the observed stronger ENA emissions in the direction opposite to the solar wind convective electric field result from a stronger proton flux in the same direction at the lower magnetosheath; i.e., the proton fluxes in the magnetosheath are not cylindrically symmetric. We also confirm the observed increasing of the ENA fluxes with the solar wind dynamical pressure in the simulations. This feature is associated with a low altitude of the induced magnetic boundary when the dynamic pressure is high and the magnetosheath protons can reach to a denser exosphere, and thus, the charge exchange rate becomes higher. Overall, the analysis suggests that kinetic effects play an important and pronounced role in the morphology of the hydrogen ENA distribution and the plasma environment at Mars, in general.

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Planetary ENA imaging: Effects of different interaction models for Mars

Cited by 19 publications

References 13 publications

Energetic Hydrogen and Oxygen Atoms Observed on the Nightside of Mars

Energetic Hydrogen and Oxygen Atoms Observed on the Nightside of Mars

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

Emission of hydrogen energetic neutral atoms from the Martian subsolar magnetosheath

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