Photoelectrons as a Tracer of Planetary Atmospheric Composition: Application to CO on Mars

X. S. Wu; J. Cui; R. V. Yelle; Y. T. Cao; Z. G. He; F. He; Y. Wei

doi:10.1029/2020JE006441

Photoelectrons as a Tracer of Planetary Atmospheric Composition: Application to CO on Mars

X. S. Wu, J. Cui, R. V. Yelle, Y. T. Cao, Z. G. He, F. He, Y. Wei

Research output: Contribution to journal › Article › peer-review

18 Scopus citations

Abstract

Photoelectrons are an extensively studied component of planetary ionospheres which have been frequently used as a diagnostic of ambient magnetic fields. We show in this study that they also provide information on atmospheric composition via the altitude variation of photoelectron intensity at specific energies. Such an idea is applied to Mars for which a large observational sample of photoelectrons is available from the Solar Wind Electron Analyzer measurements made by the Mars Atmosphere and Volatile Evolution (MAVEN). Our analysis reveals a strong decline in photoelectron intensity from 160 to 200 km, but this trend is restricted to a narrow energy range of 10–15 eV. By employing analytical yield spectrum calculations, we derive the model variations based on different choices of the background atmosphere. We find that the presence of CO is crucial for reproducing the observed variations. This allows atmospheric CO densities to be estimated from photoelectron measurements, which are a factor of 3–7 lower than the published densities based on the MAVEN Neutral Gas and Ion Mass Spectrometer measurements and in better agreement with existing model results. In general, the usefulness of photoelectron intensity at a specific energy as a tracer of atmospheric composition relies critically on the species-dependent inelastic electron impact cross section at this energy.

Original language	English (US)
Article number	e2020JE006441
Journal	Journal of Geophysical Research: Planets
Volume	125
Issue number	7
DOIs	https://doi.org/10.1029/2020JE006441
State	Published - Jul 1 2020

Keywords

atmospheric composition
photoelectron

ASJC Scopus subject areas

Geochemistry and Petrology
Geophysics
Earth and Planetary Sciences (miscellaneous)
Space and Planetary Science

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10.1029/2020JE006441

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title = "Photoelectrons as a Tracer of Planetary Atmospheric Composition: Application to CO on Mars",

abstract = "Photoelectrons are an extensively studied component of planetary ionospheres which have been frequently used as a diagnostic of ambient magnetic fields. We show in this study that they also provide information on atmospheric composition via the altitude variation of photoelectron intensity at specific energies. Such an idea is applied to Mars for which a large observational sample of photoelectrons is available from the Solar Wind Electron Analyzer measurements made by the Mars Atmosphere and Volatile Evolution (MAVEN). Our analysis reveals a strong decline in photoelectron intensity from 160 to 200 km, but this trend is restricted to a narrow energy range of 10–15 eV. By employing analytical yield spectrum calculations, we derive the model variations based on different choices of the background atmosphere. We find that the presence of CO is crucial for reproducing the observed variations. This allows atmospheric CO densities to be estimated from photoelectron measurements, which are a factor of 3–7 lower than the published densities based on the MAVEN Neutral Gas and Ion Mass Spectrometer measurements and in better agreement with existing model results. In general, the usefulness of photoelectron intensity at a specific energy as a tracer of atmospheric composition relies critically on the species-dependent inelastic electron impact cross section at this energy.",

keywords = "atmospheric composition, photoelectron",

author = "Wu, {X. S.} and J. Cui and Yelle, {R. V.} and Cao, {Y. T.} and He, {Z. G.} and F. He and Y. Wei",

note = "Funding Information: This work is supported by the B‐type Strategic Priority Program No. XDB41000000 funded by the Chinese Academy of Sciences and the pre‐research project on Civil Aerospace Technologies No. D020105 funded by China's National Space Administration. The authors also acknowledge supports from the National Science Foundation of China (NSFC) through grants 41904154, 41525015, 41774186, and 41525016. The authors thank Robert Lillis and the other anonymous referees for their constructive comments which have improved the quality of the manuscript substantially. Funding Information: This work is supported by the B-type Strategic Priority Program No. XDB41000000 funded by the Chinese Academy of Sciences and the pre-research project on Civil Aerospace Technologies No. D020105 funded by China's National Space Administration. The authors also acknowledge supports from the National Science Foundation of China (NSFC) through grants 41904154, 41525015, 41774186, and 41525016. The authors thank Robert Lillis and the other anonymous referees for their constructive comments which have improved the quality of the manuscript substantially. Publisher Copyright: {\textcopyright}2020. American Geophysical Union. All Rights Reserved.",

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doi = "10.1029/2020JE006441",

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volume = "125",

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T2 - Application to CO on Mars

AU - Wu, X. S.

AU - Cui, J.

AU - Yelle, R. V.

AU - Cao, Y. T.

AU - He, Z. G.

AU - He, F.

AU - Wei, Y.

N1 - Funding Information: This work is supported by the B‐type Strategic Priority Program No. XDB41000000 funded by the Chinese Academy of Sciences and the pre‐research project on Civil Aerospace Technologies No. D020105 funded by China's National Space Administration. The authors also acknowledge supports from the National Science Foundation of China (NSFC) through grants 41904154, 41525015, 41774186, and 41525016. The authors thank Robert Lillis and the other anonymous referees for their constructive comments which have improved the quality of the manuscript substantially. Funding Information: This work is supported by the B-type Strategic Priority Program No. XDB41000000 funded by the Chinese Academy of Sciences and the pre-research project on Civil Aerospace Technologies No. D020105 funded by China's National Space Administration. The authors also acknowledge supports from the National Science Foundation of China (NSFC) through grants 41904154, 41525015, 41774186, and 41525016. The authors thank Robert Lillis and the other anonymous referees for their constructive comments which have improved the quality of the manuscript substantially. Publisher Copyright: ©2020. American Geophysical Union. All Rights Reserved.

PY - 2020/7/1

Y1 - 2020/7/1

N2 - Photoelectrons are an extensively studied component of planetary ionospheres which have been frequently used as a diagnostic of ambient magnetic fields. We show in this study that they also provide information on atmospheric composition via the altitude variation of photoelectron intensity at specific energies. Such an idea is applied to Mars for which a large observational sample of photoelectrons is available from the Solar Wind Electron Analyzer measurements made by the Mars Atmosphere and Volatile Evolution (MAVEN). Our analysis reveals a strong decline in photoelectron intensity from 160 to 200 km, but this trend is restricted to a narrow energy range of 10–15 eV. By employing analytical yield spectrum calculations, we derive the model variations based on different choices of the background atmosphere. We find that the presence of CO is crucial for reproducing the observed variations. This allows atmospheric CO densities to be estimated from photoelectron measurements, which are a factor of 3–7 lower than the published densities based on the MAVEN Neutral Gas and Ion Mass Spectrometer measurements and in better agreement with existing model results. In general, the usefulness of photoelectron intensity at a specific energy as a tracer of atmospheric composition relies critically on the species-dependent inelastic electron impact cross section at this energy.

AB - Photoelectrons are an extensively studied component of planetary ionospheres which have been frequently used as a diagnostic of ambient magnetic fields. We show in this study that they also provide information on atmospheric composition via the altitude variation of photoelectron intensity at specific energies. Such an idea is applied to Mars for which a large observational sample of photoelectrons is available from the Solar Wind Electron Analyzer measurements made by the Mars Atmosphere and Volatile Evolution (MAVEN). Our analysis reveals a strong decline in photoelectron intensity from 160 to 200 km, but this trend is restricted to a narrow energy range of 10–15 eV. By employing analytical yield spectrum calculations, we derive the model variations based on different choices of the background atmosphere. We find that the presence of CO is crucial for reproducing the observed variations. This allows atmospheric CO densities to be estimated from photoelectron measurements, which are a factor of 3–7 lower than the published densities based on the MAVEN Neutral Gas and Ion Mass Spectrometer measurements and in better agreement with existing model results. In general, the usefulness of photoelectron intensity at a specific energy as a tracer of atmospheric composition relies critically on the species-dependent inelastic electron impact cross section at this energy.

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Photoelectrons as a Tracer of Planetary Atmospheric Composition: Application to CO on Mars

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