Cross sections for charge-changing processes involving kilo-electron-volt H and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi mathvariant="normal">H</mml:mi><mml:mo>+</mml:mo></mml:msup></mml:math>with CO and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="normal">C</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>

Lindsay, B. G.; Yu, Wandong; Stebbings, R. F.

doi:10.1103/physreva.71.032705

Cited by 18 publications

(17 citation statements)

References 40 publications

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“…Multiplying this ratio by the charge exchange efficiency of the solar wind with planetary hydrogen upstream from the bow shock should then provide the ratio between penetrating and solar wind proton flux. Figure 3 shows that the ratio of stripping to charge exchange from laboratory measurements [Van Zyl et al, 1978;Lindsay et al, 2005;Kallio and Barabash, 2001], multiplied by a nominal 3% upstream charge exchange efficiency appropriate for solar minimum [Kallio et al, 1997], matches the observed trend. However, the data show a somewhat steeper drop in penetrating fluxes at low energy than this simple model.…”

Section: Spatial Distribution and Solar Wind Control Of Hydrogen Deposupporting

confidence: 52%

“…The observed ratio of H À to H + abundances, on the order of 1:10, suggests a similar ratio for the electron attachment and stripping cross sections (the relevant charge exchange back reactions will of course also play a role in the equilibrium fractionation). Laboratory data indeed indicate a ratio on the order of 1:10 between electron capture and electron loss cross sections for 1 keV hydrogen in CO 2 [Lindsay et al, 2005] and a ratio of 1:10 to 1:20 over a broader range of energy for N 2 and O 2 [Van Zyl et al, 1978], often used as proxies for CO 2 [Kallio and Barabash, 2001].…”

Section: Relative Charge State Abundances Of Penetrating Solar Wind Hmentioning

confidence: 99%

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MAVEN observations of solar wind hydrogen deposition in the atmosphere of Mars

Halekas

Lillis

Mitchell

et al. 2015

Geophysical Research Letters

133

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Mars Atmosphere and Volatile EvolutioN mission (MAVEN) observes a tenuous but ubiquitous flux of protons with the same energy as the solar wind in the Martian atmosphere. During high flux intervals, we observe a corresponding negative hydrogen population. The correlation between penetrating and solar wind fluxes, the constant energy, and the lack of a corresponding charged population at intermediate altitudes implicate products of hydrogen energetic neutral atoms from charge exchange between the upstream solar wind and the exosphere. These atoms, previously observed in neutral form, penetrate the magnetosphere unaffected by electromagnetic fields (retaining the solar wind velocity), and some fraction reconvert to charged form through collisions with the atmosphere. MAVEN characterizes the energy and angular distributions of both penetrating and backscattered particles, potentially providing information about the solar wind, the hydrogen corona, and collisional interactions in the atmosphere. The accretion of solar wind hydrogen may provide an important source term to the Martian atmosphere over the planet's history.

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Section: Spatial Distribution and Solar Wind Control Of Hydrogen Deposupporting

confidence: 52%

Section: Relative Charge State Abundances Of Penetrating Solar Wind Hmentioning

confidence: 99%

MAVEN observations of solar wind hydrogen deposition in the atmosphere of Mars

Halekas

Lillis

Mitchell

et al. 2015

Geophysical Research Letters

133

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“…[] and Lindsay et al . [], we expect an equilibrium charged fraction

F_{eq}^{+}

of ~4–15% for typical solar wind speeds, with higher charged fraction for larger speed. The neutral column density required for convergence is ~1/( σ 01 + σ 10 ) or ~10 15 cm −2 for typical solar wind speed.…”

Section: Precipitating Hydrogen Observationsmentioning

confidence: 93%

Seasonal variability of the hydrogen exosphere of Mars

2017

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The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission measures both the upstream solar wind and collisional products from energetic neutral hydrogen atoms that precipitate into the upper atmosphere after their initial formation by charge exchange with exospheric hydrogen. By computing the ratio between the densities of these populations, we derive a robust measurement of the column density of exospheric hydrogen upstream of the Martian bow shock. By comparing with Chamberlain‐type model exospheres, we place new constraints on the structure and escape rates of exospheric hydrogen, derived from observations sensitive to a different and potentially complementary column from most scattered sunlight observations. Our observations provide quantitative estimates of the hydrogen exosphere with nearly complete temporal coverage, revealing order of magnitude seasonal changes in column density and a peak slightly after perihelion, approximately at southern summer solstice. The timing of this peak suggests either a lag in the response of the Martian atmosphere to solar inputs or a seasonal effect driven by lower atmosphere dynamics. The high degree of seasonal variability implied by our observations suggests that the Martian atmosphere and the thermal escape of light elements depend sensitively on solar inputs.

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“…After examining our data, we find that profiles measured at higher altitudes do indeed have a higher background on average than those collected deeper in the ionosphere of Mars, which may be contributing to the behavior we see in panel c of Figure 6. We do not believe that the discrepancy between the theoretical and observed value is due to any errors in the cross sections calculated by Van Zyl et al (1978) and Lindsay et al (2005), but rather due to a data processing issue or unknown physical process. It is unclear why the penetrating protons seem to take such a long time to reach this equilibrium fraction.…”

Section: Column Densitymentioning

confidence: 74%

Precipitating Solar Wind Hydrogen as Observed by the MAVEN Spacecraft: Distribution as a Function of Column Density, Altitude, and Solar Zenith Angle

Henderson¹,

Halekas

Lillis

et al. 2021

JGR Planets

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Because it lacks a global magnetic field, Mars's atmosphere is subject to direct interaction with the solar wind, which can provide energy for atmospheric constituents to escape the planet's gravitational pull through a variety of processes, including photochemical escape, sputtering, and pick up ion escape Lillis et al., 2015). Evidence suggests that this solar wind interaction has played a major role in changing Mars from a warm, water rich environment to the cold, dry planet we observe today (Jakosky et al., 2018). Mars's atmosphere is comprised primarily of CO 2 but also exhibits a hydrogen corona that extends past the planet's bow shock (Anderson, 1974;Anderson & Hord, 1971). This hydrogen corona is subject to direct interaction with the solar wind by means of charge exchange, providing us with a unique laboratory to observe and characterize various phenomena within the upper Martian atmosphere.As solar wind protons propagate toward Mars, they can charge exchange with neutral hydrogen atoms in the planet's corona, resulting in energetic neutral atoms (ENAs) with the solar wind speed (Kallio et al., 1997). These ENAs can then travel toward the planet without being affected by electromagnetic forces and thus

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Cross sections for charge-changing processes involving kilo-electron-volt H andH+with CO andCO2

Cited by 18 publications

References 40 publications

MAVEN observations of solar wind hydrogen deposition in the atmosphere of Mars

MAVEN observations of solar wind hydrogen deposition in the atmosphere of Mars

Seasonal variability of the hydrogen exosphere of Mars

Precipitating Solar Wind Hydrogen as Observed by the MAVEN Spacecraft: Distribution as a Function of Column Density, Altitude, and Solar Zenith Angle

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