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

Holmström, M.; Barabash, S.; Futaana, Yoshifumi; Grigoriev, Alexander; Würz, Peter

doi:10.1002/2014ja020307

Cited by 10 publications

(12 citation statements)

References 43 publications

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“…The H‐ENA diagnostics allow remote imaging of the neutral density distribution and plasma flux distribution. At Mars, the H‐ENA imaging has revealed a deflection of solar wind protons at the subsolar point (Futaana, Barabash, Holmström, et al, ), a global asymmetry in the magnetosheath proton flow (Wang et al, , ), and oscillations of the magnetospheric plasma flow (Grigoriev et al, ). We will show in section that the precipitating H‐ENAs can be used to constrain the exospheric density of Mars and its annual variability.…”

Section: Introductionmentioning

confidence: 99%

Precipitation of Hydrogen Energetic Neutral Atoms at the Upper Atmosphere of Mars

et al. 2018

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We study the properties of neutral hydrogen atoms precipitating onto the upper atmosphere of Mars. Energetic neutral atoms (ENAs) are produced by the charge exchange process between protons of solar wind (both upstream and shocked) as well as planetary origins and the Martian exospheric neutrals. Using a global hybrid plasma model for Mars-solar wind interaction combined with an up-to-date exosphere model of Mars, we calculate the fluxes, spatial distributions, energy spectra, and direction distributions of hydrogen ENAs (H-ENAs) at the Martian exobase for each source proton population. H-ENAs originating from the upstream solar wind region and the magnetosheath dominate the precipitation. Two percent of the solar wind flux penetrates through the magnetic barrier as H-ENAs under solar minimum conditions. The precipitating solar wind H-ENA flux is axially symmetric about Sun-Mars line, while the magnetosheath and planetary H-ENAs have higher fluxes and a more-extended precipitation area in the hemisphere where the convection electric field is pointing away from the planet, causing a significant precipitation beyond the terminator. The observed asymmetry is consistently explained by an asymmetric plasma flow in the dayside magnetosheath. The solar wind dynamic pressure increases the solar wind H-ENA precipitation normalized by the upstream proton flux, due to a closer bow shock position and thus a higher exospheric column density for charge exchange. The spatial distribution of the magnetosheath solar wind and planetary H-ENAs becomes more axially symmetric with increased dynamic pressure. The solar wind interaction with Mars exhibits more gas-dynamic-like signatures for higher dynamic pressure.

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Section: Introductionmentioning

confidence: 99%

Precipitation of Hydrogen Energetic Neutral Atoms at the Upper Atmosphere of Mars

et al. 2018

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“…These processes result in angular spreading, energy deposition, and backscattering of a fraction of the precipitating flux of H ENAs (Kallio & Barabash, 2001;Shematovich et al, 2011). These hydrogen ENAs, together with H atoms produced in the solar wind and magnetosheath (Gunell et al, 2006) and the backscattered population (Futaana et al, 2006;Mura et al, 2008;Wang et al, 2013Wang et al, , 2014, were observed in the Martian system by the ASPERA-3 instrument onboard MEX. A fraction of the hydrogen atoms (both incoming and backscattered) interact with the atmosphere in charge-exchange reactions and become protons again.…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo Simulations of the Interaction of Fast Proton and Hydrogen Atoms With the Martian Atmosphere and Comparison With In Situ Measurements

et al. 2018

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We present model results of the interaction of proton and hydrogen atom precipitation with the Martian atmosphere. We use a kinetic Monte Carlo model developed earlier for the analysis of the Analyzer of Space Plasmas and Energetic Atoms (ASPERA‐3) Mars Express data. With the availability of Mars Atmosphere and Volatile Evolution Mission in situ measurements, not only the flux of protons incident on the atmosphere but also their degradation along the orbit may now be described. The comparison of the simulations with data collected with the Solar Wind Ion Analyzer shows that the Monte Carlo model reproduces some of the measured features. The results of comparison between simulations and measurements of the proton fluxes at low altitudes make it possible to infer the efficiency of charge exchange between solar wind and the extended hydrogen corona if the value of the magnetic field is measured simultaneously. We also find that the induced magnetic field plays a very important role in the formation of the backscattered flux and strongly controls its magnitude. At the same time, discrepancies between the modeled and the measured energy spectra of the backscattered protons are pointed out. We suggest that some of the physical processes controlling the upward flux are not fully understood or that the data processing of the measured backscattered proton flux should be improved.

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“…These models have been used to understand an extensive array of Martian plasma processes and interactions. Plasma boundaries (Bertucci et al, ; Bößwetter et al, ; Najib et al, ), spatial ion distribution (Najib et al, ), ion escape (Brecht et al, ; Brecht & Ledvina, ; Dong, Fang et al, ; Fang et al, ; Kallio, Fedorov et al, ), magnetic topology (Liemohn et al, ), energetic neutral atoms (ENAs; Gunell et al, ; Kallio, Barabash et al, ; Wang et al, , ), solar wind alpha particles (Chanteur et al, ), and X‐ray emission (Gunell et al, ) have all been studied using Martian plasma models. Transient processes including coronal mass ejection (CMEs; Dong, Ma, et al, ; Ma et al, ), changes in dynamic pressure (Ma et al, ), changes in solar extreme ultraviolet (EUV) flux (Modolo et al, , ), seasonal variation (Dong et al, ), and crustal field rotation (Fang et al, ; Ma et al, ) have also been topics of study.…”

Section: Introductionmentioning

confidence: 99%

Comparison of Global Martian Plasma Models in the Context of MAVEN Observations

Egan

Dong

et al. 2018

JGR Space Physics

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Global models of the interaction of the solar wind with the Martian upper atmosphere have proved to be valuable tools for investigating both the escape to space of the Martian atmosphere and the physical processes controlling this complex interaction. The many models currently in use employ different physical assumptions, but it can be difficult to directly compare the effectiveness of the models since they are rarely run for the same input conditions. Here we present the results of a model comparison activity, where five global models (single-fluid MHD, multifluid MHD, multifluid electron pressure MHD, and two hybrid models) were run for identical conditions corresponding to a single orbit of observations from the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. We find that low-altitude ion densities are very similar across all models and are comparable to MAVEN ion density measurements from periapsis. Plasma boundaries appear generally symmetric in all models and vary only slightly in extent. Despite these similarities there are clear morphological differences in ion behavior in other regions such as the tail and southern hemisphere. These differences are observable in ion escape loss maps and are necessary to understand in order to accurately use models in aiding our understanding of the Martian plasma environment.

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

Cited by 10 publications

References 43 publications

Precipitation of Hydrogen Energetic Neutral Atoms at the Upper Atmosphere of Mars

Precipitation of Hydrogen Energetic Neutral Atoms at the Upper Atmosphere of Mars

Monte Carlo Simulations of the Interaction of Fast Proton and Hydrogen Atoms With the Martian Atmosphere and Comparison With In Situ Measurements

Comparison of Global Martian Plasma Models in the Context of MAVEN Observations

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